Since there are some rumors about 32SP-clusters, could be the number after GT2 the number of clusters, so GT212 with 384SPs and 96TMUs?
Even tough it´s not a well kept secret that NV has to be more aggressive WRT process-node adoption in the coming months, I´m extremely sceptical that NV wants such a beast on the 40nm (40G) node this early. I´m not sure if NV wants to play the "delay", "bad margins" and "power consumption" game again.
They need something less complex than a GTX280, but faster, with 8800
GT-like qualities, e.x. lower power consumption and less noise (and this time, good yields, too).
Which is exactly what I think the roadmap shows. It says
GT206 and
GT212 and not
GTX anymore.
Also, don´t forget that NV needs something to compete with a possible, future AMD/ATI´s X2 solution, based on RV8xx, which AMD/ATI is definately not going to abandon.
On 40nm you can have an extremely good mix of complexity, clocks and efficiency if you are gonna design it around that node. Why not use that to your advantage?