Points 1, 2 and 4 are IMO becoming less relevant.
With regard to point 3, when hardcore gamers see and understand the benefits they will look at the PS3 as offering better value.
For the lowend casual market, the 360 will be competing with cheaper more casual products like the Wii and PS2.
But overall I think 2008 will still be an OK year for the 360, 2009 I think the platform will be hurting very much (like HD DVD is hurting now).