Most developers have been pretty tight-lipped about the pricing they've chosen for their upcoming games and applications. Before today, we'd only heard from 3 game developers who had chosen a price for their upcoming games.
The prices for those games were Trism ($4.99), Lumen ($5.00) and Aki Mobile Mahjong ($9.99). Arguably the two games priced around $5 come from relatively small developers, while Aki comes from long established Mac developer, Ambrosia Software.
iPhone and iPod Touch games will be distributed directly from Apple's iTunes App store with 70% of the revenue going to the developer. About $7 of each $9.99 title will go to the developers, while only $3.50 of a $5 application.
I suspect with this precedent established, most established game developers will target their games around the $9.99 price point, while leaving room for less well established developers to shoot for more value with closer to $5 prices.