What it should be - when the PS4 comes out
When it probably will be - November 2013
PS4 will be the last to be announced out of the next gen consles. Xbox's new consle is to be announced late 2013.
I think the game will sell enough to warrant a sequel. You only need over 1 million to be sure (basing it off other games that got sequels). Based on preorder lists/best seller lists, this game will sell that amount easily.
I think a sequel will be on PS4 and will come out in winter of 2014 or winter of 2015. 2-3 years is a standard development cycle, but that could change with a new console.