A couple of weeks before the big Maxwell release, Nvidia dropped the GTX 770 to $329. That is the same price at which the GTX 970 debuted. As part of the Maxwell launch, the official GTX 760 price was dropped to $219. Thus, I suspect that the GTX 960 may come in at that same $219 price point when it launches.
I expect that the GTX 960 will have a purpose-built smaller chip (GM206) rather than using a further cut-down GM204, since 28nm yields are high enough that there probably won't be enough die-salvaged parts to meet the demand. There's certainly room for a third chip between GM107 and GM204. I suspect it will have 1280 stream processors - double what the GM107 has, but still comfortably below the cut-down GM204. Probably 32 ROPs and a 192-bit memory bus.
This kind of release would put a lot of pricing pressure on AMD while maintaining high profits - the chip and board will both be inexpensive and easy to produce, and TDP probably won't go past 125W or so. Only one six-pin PCI-E connector should be required, except for heavily overclocked models.
Performance will be better than GTX 770 (two Maxwell SPs seem to be about equivalent in power to three Kepler SPs). It should also comfortably beat the AMD R9 280X.