I think the next console also will be 1080p. You might get a few scaling tricks under the hood to output at 4k but my guess is we will still be dealing with a 1080p image in the first instance with loads of advanced post processing to bring the image up to scratch for newer tvs.
As for memory, I don't see it going up a great amount. I'd be amazed at any more than 16gb personally, its frankly just not needed. Quite why the operating systems of the current consoles require over 3gb is absolute beyond me, it seems like massive overkill for requirements of what is in a nutshell a very very basic OS.
What I would expect next time though is 1080p/60 without question. The GPU on the new ones you guess would be equivalent of the absolute top end GPU's of PCs today which carve through games with ease (and would do even more so with the optimisations that consoles get in favour of PC games.)
PREDICTIONS FOR END OF 2015: (Made Jan 1st 2015)
PS4 - 34M - XB1 - 21m - WII U -12M
