Should it be? I think so.
Will it be? Quite honestly I can't see anyone from 2K going down that road, the NBA games had both gens this past year but that said, Next Gen was basically an entirely different game, they could do the same thing here.
While NBA 2k14 and WWE 2k15 have Visual Concepts as the common denominator I would seriously be surprised (pleasantly ofcourse) if it looked just as good.
Just to clarify, Yukes is till lead developer so don't expect any ground breaking gameplay changes, Visual Concepts could bring awesome graphics to the table. Unlikely but one can hope.
I am hoping there will be a career mode where I can take my CAW from NXT to main eventing multiple wrestlemanias (not gonna happen, but again, here's to hoping)