No, Xscapes performance isn't why. It performed pretty well and had a hit. I don't think they could have reasonably hoped for more. I think the Estate is pacing this thing out. People like to bag the Estate because we want everything at once - and I don't love some of the decisions they've made, but let's compare the Elvis estate and Michael Jackson for a minute.
It took Elvis 46 years to get a biopic - its taking Michael 15. Elvis took about 30 years to have a posthumous hit. Michael, what, 5? Michael has had two posthumous albums, Elvis none I believe? Michael has arguably had more stageshows officially pushed by the Estate. The Estate has been behind the Thriller 40 documentary, how many documentaries does Elvis have?
I think you get my point. If someone could bother comparing what Elvis has got in 47 years since his death compared to Michael you'd find, comparatively, Michael fans have been absolutely spoiled.
The long game is that there will definitely be more posthumous albums. They didn't spend a billion dollars on his vault just to let the thing rot. There is so much material and a lot of it will be meaningful in 20, 30, 40, 50 years. Not only do they have his songs but some unreleased film clips, writings, plans, poems, list goes on and on. I think the Estate has sometimes missed the mark on some things but they're thinking the long game.