It's hard to tell whether the price on these will drop or go up because it has no real competition between $99 and $119.
It will drop. It's very very rare for video cards or any technology to increase in price over time. And there is competition of course, between the various vendors, even if the card itself has no direct competition from Nvidia.
Well, the 4850/GTS 250 will definitely beat the 4770 as seen in Toms' benchmark. With the 4870 available for $140, I don't really see any point in getting a 4770 other than for the power factor. For $30 more, you get GDDR5 with a higher clock, 256-bit bus and overall, the 4870 is still a better choice, if you ask me.