next year would be a good time to get a head start, especially if they can get AMDs next gen part a year earlier
Xbox's GPU (via Nvidia) was basically an early GeForce 4 Ti4400 (which launched April 2002) and before someone tears me up, yes it was a GeForce 3 with two pixel pipelines, which is basically what a GeForce 4 was... except with DX8.1 support... and other stuff.
Xbox 360 GPU was roughly a very early HD2000/3000 (launched in 2007)
They have done it before, we don't know exactly how much R&D is going into this thing.
for the time it was a pretty radical design but later we saw it was the future foundation of the Radeon line. there was nothing quite like it out there, especially in flexibility
but in regards to future tech... I would assume because of the universal shading pipeline that has existed since the Xbox 360 GPU... it's likely the most improvements would be to floating point precision, general performance increases and performance:watt. We haven't seen the universal shaders mature, not even close.