The following is speculative, and should not be considered based on any non-public information, as it quite simply is not so!
The codenames used are most certainly incorrect, and some might not even have their own codenames. As such, they are used exclusively to permit further discussion, and nothing else!
February->March 2007
G81: Optical shrink of G80 on 80GT (G80 currently is on 90GT - R600 is either on 80GT or 80HS). Introduces the 7/8 clusters SKU. Exact specifications (identical to G80 on 90GT or not; GDDR4 or not; etc.) depend on the R600's specifications. 1.1GHz GDDR4 and 600-625MHz is possible, if considered necessary. If such a step is taken, the parts with redundancy would likely also use GDDR4, which would define the 8900 line-up. There will NOT be a notebook version.
G82: G8x on 80GT with 6 native clusters and 5 native ROP partitions. Can act as a 8800GTS (which will then cost $399) or a 8700-series GPU, which would likely have 5 active clusters, 4 active ROP partitions and a 256-bit memory bus. This is needed for the 8800(/8900?)GTS, as G81 will mostly be 8/7 cluster parts due to improved yields with the smaller 80nm die. There will be a notebook version. Maybe pin-compatible with G81(?)
G83: G8x on 80GT(?) with 4 native clusters and 2 native ROP partitions. 192-bit memory bus and roughly $199 target introduction price. 8600/8500-Series, possible version with 3 active clusters.
March->May 2007
G84: G8x on 80GT(?) with 3 native clusters and 2 native ROP partitions. Version with 2 active clusters and 2 native ROP partitions. 128-bit memory bus. 8400/8300-Series. Maybe pin-compatible with G83(?)
G8i: G8x-based Intel IGP on 80GT(?) with 1 native cluster and 1 ROP partition, that has even less blending units, maybe no extra double-z, etc.(?)
G8a: Same as G8i, but for AMD's socket AM2.
June->August 2007
G85: G8x on 65nm, 2 native clusters and 1 native ROP partition. Sold at ~$99. Finally replaces G73's 80nm shrink. G72's 65nm shrink will already have been released for some time, and will remain in heavy production for the ultra-low-end SKUs.
September->December 2007
G90:
65nm, Q4 2007; 400mm2+
1.4-1.6GHz GDDR4, 384-bit Bus
1.45-1.75GHz Shader Core Clock
6 ROP partitions, but beefier
625-675MHz Core Clock
FP64 Support (Slow!)
32 MADDs/Cluster
24 Interps/Cluster
10 Clusters
Q1->Q2 2008
G91: 7(?) native clusters, 65nm
G92: 4(?) native clusters, 65nm
Q2->Q3 2008
G9I/A: 2(?) native clusters IGPs, 55nm(?) (competes with Fusion?)
G93: 3(?) native clusters, 55nm(?); replaces G85
Q4 2008
G94: 7(?) native clusters, 55nm(?)
G95: 12(?) native clusters, 55nm(?); 9900-Series
G96: 4(?) native clusters, 45nm(?); G93 moves into the ultra-low-end
Q2 2009
G100: ...
BTW, in terms of Quad-SLI, I think you're much more likely to see those with G82 and G91 than with G81 or G90. That's still a hefty performance gain, and would be much more reasonable in terms of power consumption.
Uttar