I'm sure we'll have a Nexus "3" or whatever, likely next winter. I would guess that it has a dual-core CPU as well. I would guess that it will be out on Sprint, given native Google voice and T-Mobile's buyout.
What's more interesting is if it will be manufactured by Samsung or HTC (or others, even). Most likely its Samsung or HTC since they make WiMax phones for Sprint.
I would guess the Nexus 3 to be like the Galaxy 2 if made by Samsung (Super AMOLED plus, dual core Samsung CPU) or the HTC Pyramid (dual core qualcomm, qHD).
It's a stretch, but I'm going to guess that it will be Samsung - because I feel Google's pure Android is leaning more and more towards OLED, where Samsung excels.
Not sure how tough the Nexus S contour display is, but I wouldn't complain about a return to Gorilla glass, and a Galaxy S equivalent car dock would be nice.