I strongly disagree that this game, or any fps for Xbox 360, will withstand it's strong online community once Halo 3 is released. I'm not bashing, I'm just not daydreaming. Before Halo 2 came out, many people were convinced that what they had at the moment for Xbox Live was what would stay as the best thing for online console gaming and the reason why people play online against real people. They were proved wrong, with Halo 2 increasing Xbox Live subscriptions dramatically.
When Socom 2 came out for ps2, it was all everyone with an online connection would play for many reasons (some obvious to those who have experienced Xbox Live). Once the experienced dimmed down around a year ago, many started to play Timesplitters: FP, saying that it was the new socom of online gaming. Once Socom 3 came out, everyone forgot what they said about Timespitters and returned to their days of socom.
I'm not saying PD0 is like timesplitters in that respect, but I'm just giving you an example of how gamers are with what's the 'hot thing' at the moment.
PD0 will still be a great online game with a great community when Halo3 is out, but don't think that Halo 3 won't be the new Halo 2 in terms of being the 'hot thing' over Xbox Live, or for Xbox 360 in general.
Like I said, I'm just being realistic.