"I think you could take the concept out of the stadiums and you could do Winter Sanitarium," Ulrich told Launch. "I mean there's a lot of things you could do with the name Sanitarium. So, I just don't want to get stuck into kind of stadiums in the summer because obviously that's a special thing every couple three, four, five years or whatever when it feels right. And after this tour, which is obviously turning out awesome, but now we want to play indoors."

The Launch article speculated that the band was in the process of setting up North American arena tour dates to kick off in February. 

more on Metallica

Preview and purchase music from Metallica