Confirmations from various articles reveal that the KZ3 controls are greatly refined. The hands-on impressions from one site says they work great so far. BTW, you'll likely be able to play with the Move controller for more accuracy as well.
Also, they are adding two player full game co-op, as well as four-player campaign episodes (probably similar to Resistance 2's co-op). Every single area in the game is supposed to have a variety of visuals (including colorful lush jungles, space fighting and snow storm areas) to avoid the problem of muted color issue of KZ2. A game level in KZ3 is 10x the size of a level in KZ2, and the game play is a lot more action based and less stealth based.
The developers say there are varied set pieces everywhere from start to finish so that you aren't just doing the same stuff over and over. Also, the melee gameplay will be a very big part of KZ3, with all new deep mechanics and brutal animations. Jetpacks, first seen on enemies in the PSP game Killzone Liberation, will be accessible by players in this sequel.
The graphic engine is getting a significant upgrade, in part due to help from Naughty Dog (Uncharted 2 developers). The sound engine is also getting overhauled to produce top tier SFX. The designers also confirm that there will be no gratuitous profanity like KZ2.
I'm really looking forward to seeing the first trailer for this one.
