Let me just fix that...
What do you think?
What do you think will happen in Weirdmageddon Part 2?
I think the prison bubble is like the time bubble thing that Blendin (well, Bill possessing Blendin) was talking about.
So the prison bubble would be summer in Gravity Falls, only it would last forever.
And Mabel would be in there and she wouldn't want to leave even though she knows it's not real