Are the GT200 and R700 new gpu's or not?
Well the basic designs aren't. The actual gpu's are new ofcourse.
History:
R300 => R420 => R520
ATI used the basic R300 design from august 2002 until R600 was released (may 2007 but should have been on the market 6 months earlier without delay).
NV40 => G70
nVidia used NV40 technology from april 2004 until november 2006.
So it's quiet common to use certain technology for a couple generations. This will be even more profound with current generation of gpu's because of the increased complexity of unified shaders.
It takes 2 to 3 years to design a gpu like the R300, NV40, R600 or G80. After that you get the usual updates. Even a process shrink, let's say 65nm to 45nm, takes almost a year without even touching the design. These companies manage to hide this time because they have multiple design teams working in parallel.
The same thing happens with cpu's. Look at K8 and K10. Look at Conroe and Penryn.
Expect really new architectures from ATI and nVidia somewhere in 2009, maybe even later and they will be DX11.