Xbox 360 was around 12 million when Halo 3 released. PS3 should be over 8 mil at the end of this year. MGS4 is going to be released in second quarter of 2008 (acording to wiki, this of course may change in future). This means PS3 will have 13-26 weeks in 2008 before MGS4 releases, let's assume it's 20 weeks. So if PS3 will be selling around 150k per week in first 20 weeks of 2008 it will be at more than 11 million when MGS launches. It's close to Xbox 360 number when Halo 3 launched. So the userbase probably won't be as big (of course I may be wrong and 150k per week may be to high but if GTA won't be deleayed that 150k may be even to low).
Hovewer I think that what Halo 3 did on its userbase was really amazing and will be really hard to do again.







