With Blu-Ray on the verge of winning the war, expect a price cut on the PS3 when MGS4 is launched. Why? Because Sony knows money will be coming in from Blu-Ray licensing. Also GTA4 will move more PS3's than 360, as will DMC4. Why? Well look at how many consoles Halo 3 moved...or didn't move.
The PS3 will outsell the 360 WW, but match the weekly 360 sales in NA after March. Also, don't underestimate the adoption rate of Blu-Ray, it still could spur more PS3 sales.
1. Halo 3 did spur console sales.
2. If there is any one title likely to kick old PS2 owners into the new generation, it's GTA4. The question is where does there loyalty lie? With Sony? They'll go PS3. With GTA? They'll go for the exclusive content on 360. With their wallets? 360 again.