The specs seem to be insane.
2GB RAM is overkill AND expensive.
Its simply not possible to have 512Mbit memory, 256 shaders on the same chip on 65nm.
That chip would be 2-3 times bigger than current chips and would contain more than 1 billion shaders. Not possible on 65 nm.
It would be way too hot and it will never be possible to clock the chip at 780Mhz.
For these kind of specs, transition to 32nm is required atleast. Even 45nm is a bit less to achieve these high clocks on a chip that large.
There is a possibility though if the chip is not a single core chip, but a chip with four cores with 64 shaders and 128bit mem interface each.
Overall, the specs seem too good to be true in the next 2 years.