If you want to avoid my post, bottom line is Nvidia is not in trouble at all, in fact it is in a much better position than it was with GF100.
Nvidia and AMD have several teams working on different chips and generations of chips, so the fact that one chip is late doesn't affect others. It does shake the next releases a bit but mostly from a marketing standpoint, as they first want to sell some high-end chips, before they release the perf/price king (i.e GF100->GF104 == G80->G92). The original schedule in Nvidia was GF100 in Q4 2009, GF104 in Q1 2010 and mainstream/entry in Q2, rinse and repeat with next gen starting in Q4 2010. So basically GF100 was late by 6+ months, GF104 was late by 3 months and GF106 by 2 months or so. Next gen is not going to be late necessarily or too late, i.e Q1 2011 release. Remember that Nvidia doesn't need any re-design at the moment, they just need to add clusters or SIMDs to GF104 and have a "winner" in comparison to GF100 and that should be enough to compete with HD6000 cards.
For example, without engineers et all thinking too much (nothing at all actually
), adding one more cluster to GF104 you end up with a chip slightly smaller than GF100 (less than 3 billion transistors against the 3+ billion in GF100) but with significantly better specs:
Shaders: 480 SP -> 576 SP, 20% increase*
texture units: 64 TMU -> 96 TMU, 50% increase*
ROP: 48 same*
memory: 384 bit same*
* That's without taking into account that GF104 clocks much better than GF100, the new chip could be clocked at 800 Mhz easily and that would mean the new chip would be 30-40% faster than the GTX480, soundly beating the HD5970 and probably the HD6870 by the same ammount as the GTX480 beats the HD5870, except this time Cayman is said to be 400mm and NV chip would be a bit smaller than GF100.
On top of that and considering that finally TSMC's 40nm is at same yields as 55nm, Nvidia could decide to take the risk and instead of releasing a slightly smaller chip, they could go with a slightly bigger, but yummy yummy, chip. How? Same chip as mentioned above except they'd add one more SIMD to the SMs (note how small a cange this is and how easy to engineer/release it would be). GF104 is superscalar and its SMs have 3 SIMDS while having 2 schedulers, wasting one scheduler every odd clock cycle because it has no SIMD unit to talk to. The jump to 4 SIMDs at some point is unavoidable then, why not do it now, taking a small risk**? End result (and compared to GTX480):
764 SPs (+60%), 96 TMU (+50%), 48 ROPs, 384 bit. 750 Mhz...
** Small, because at this point 40nm yields are good, they know the process better and the resulted chip I estimate it would have 3.2 billion transistors and be smaller than GT200 in 65nm. That is, it wouldn't be the biggest chip Nvidia has made, but the benefits are enormous.