The boxset will include all four feature films in the series as well as separate bonus disc for each movie loaded with extras. Wait, the movies are loaded with extras as well. 

For about a hundred bucks you get: 

Alien – original theatric version or new director’s cut. 

Aliens – original theatric version or special director’s cut. 

Alien 3 – includes over 30 minutes of new footage. 

Alien Resurrection – with alternate ending and opening scenes. 

In all the box set feature 45 hours of never-before-seen footage including the alternate cuts and the requisite bonus features including new director commentaries, original screen tests,  a multi-angle look at the "Chestburster" sequence from Alien, Easter eggs, deleted scenes, featurettes on casting and creature design, plus production footage. 

Here are all the details from the official press release: 

"ALIEN"
     *  The original 1979 theatrical version of "Alien" and the 2003
        Director's cut
     *  An introduction by Director Ridley Scott, Dan O'Bannon, Sigourney
        Weaver, Veronica Cartwright, Harry Dean Stanton, John Hurt and more
     *  Brand new commentary by Ridley Scott and the technical crew
     *  Nine brand new documentaries: "Star Beast" -- On developing the
        "Alien" story; "The Visualists" -- the direction and design of the
        film; "Truckers In Space" -- Casting the movie; "Fear Of The Unknown"
        -- Behind the scenes at Shepperton Studios in 1978; "The Darkest
        Reaches" -- Developing the Nostromo and Alien planet; "The Eight
        Passenger" -- Creating the Alien; "Future Tense" -- Focusing on the
        music and editing of "Alien;" "Outward Bound" -- Peering into the
        film's visual effects; "A Nightmare Fulfilled" -- Reaction to the
        film's opening
     *  A Multi-Angle Scene Study on the Chestburster sequence with optional
        commentary by Ridley Scott and the production team
     *  Sigourney Weaver's original screen test with optional commentary by
        Ridley Scott
     *  Seven deleted scenes with a deleted footage marker and deleted scene
        index
     *  The first draft of the screenplay by Dan O'Bannon
     *  Ridleygrams -- Original thumbnails and sketches by Ridley Scott
     *  Storyboard Archives
     *  The Art of "Alien" including a cast portrait gallery, production
        gallery, the sets of "Alien," H.R. Giger's Workshop, continuity
        polaroids and VFX gallery
     *  The original theatrical posters and stills from the premiere
 

     "ALIENS"
     *  The original theatrical version -- available for the first time ever
        on DVD -- and James Cameron's special edition version of "Aliens"
     *  An introduction by Director James Cameron
     *  Brand new commentary by James Cameron, Michael Biehn, Jenette
        Goldstein, Carrie Henn, Terry Henn, Lance Henriksen, Gale Anne Hurd,
        Pat McClung, Bill Paxton, Dennis Skotak, Robert Skotak and Stan
        Winston
     *  James Cameron original treatment
     *  Nine brand new featurettes: "57 Years Later" -- Continuing the saga;
        "Building Better Worlds" -- From concept to construction; "Preparing
        For Battle" -- Casting and characterization; "This Time It's War" --
        A look back at Pinewood Studios, 1985; "The Risk Always Lives" --
        Weapons and action; "Bug Hunt" -- Creature design; "Beauty And The
        Bitch" -- Power Loader vs. Queen Alien; "Two Orphans" -- Revisiting
        Sigourney Weaver And Carrie Henn; and "Aliens Unleashed" -- Reaction
        to the film
     *  The Art of "Aliens" including conceptual art portfolio, cast
        portraits, production gallery, continuity polaroids, Stan Winston's
        workshop, VFX gallery and premiere stills
     *  Deleted footage marker and deleted scene index
     *  Multi-angle videomatics with optional commentary by Miniature Effect
        Supervisor, Pat McClung
     *  An Easter Egg
 

     "ALIEN 3"
     *  The original theatrical version and a restored pre-release version
        with more than 30 minutes of never-before-seen footage
     *  Brand new commentary by Cinematographer Alex Thompson, Editor Terry
        Rawlings, VFX Designers Alec Gillis and Tom Woodruff Jr., Visual
        Effects Producer Richard Edlund, and actors Paul McGann and Lance
        Henriksen
     *  11 new featurettes: "Development" -- Concluding the story; "Tales Of
        The Wooden Planet" -- Vincent Ward's vision; "Pre-Production III" --
        The making of "Alien 3;" "Xeno-Erotic" -- H.R. Giger's redesign of the
        Alien creature; "Production: Part One, Part Two, and Part Three" --
        Behind-the-scenes on the production of the movie; "Adaptive Organism"
        -- Creature design; "Optical Fury" -- Visual effects; "Music, Editing
        And Sound"; and "Post-Mortem" -- A reaction to the film
     *  E.E.V. Bio-Scan -- A multi-angle vignette with optional commentary by
        Alex Gillis
     *  The Art of "Alien 3" including conceptual art portfolio, production
        gallery, and visual effects
     *  Furnace construction time lapse
     *  Storyboard archives
 

     "ALIEN RESURRECTION"
     *  The original theatrical version and an extended cut with alternate
        opening and ending sequences
     *  An introduction by Director Jean Pierre Jeunet
     *  Brand new commentary by Director Jean Pierre Jeunet, Herve Schneid,
        Alec Gillis, Tom Woodruff Jr., Pitof, Sylvain Despretz, Ron Perlman,
        Dominique Pinon and Leland Orser
     *  First draft of the screenplay by Joss Whedon
     *  11 new featurettes: "From The Ashes" -- Reviving the story; "French
        Twist" -- Direction and design; "Under The Skin" -- Casting and
        characters; "Death From Below" -- Underwater photography; "In The
        Zone" -- Basketball scene; "Unnatural Mutation" -- Creature design,
        "Genetic Mutation" -- Creature design; "Genetic Composition" -- A
        listen to the music; "Virtual Alien" -- Computer generated imagery; "A
        Matter Of Scale" -- Miniature photography; and "Critical Junction" --
        A reaction to the film
     *  Multi-angle rehearsal footage
     *  A Mike Carro photo gallery, a conceptual art gallery, VFX gallery, a
        promotional photo archive and continuity polaroids
     *  Storyboard archives
     *  An Easter Egg
 

     BONUS DISC
     *  A brand new Q&A with Ridley Scott
     *  "Experience in Terror" -- A promotional featurette from 1979
     *  "Alien Evolution" -- Channel 4 U.K. exclusive documentary on "Alien"
     *  A complete laser disc archive of "Alien" and "Aliens"
     *  Original theatrical trailers and TV spots from all four films
     *  "Aliens In The Basement" -- Inside the Bob Burns "ALIEN" Collection
     *  Dark Horse cover gallery -- Anthology of 11 issues of the "ALIEN"
        comics
     *  DVD-ROM feature -- Script to screen comparisons