My guess on why Sin and Punishment 2 isn't coming out Q1 is because Nintendo isn't going to have any major titles for Q2 and so they're delaying it for then. I mean, out of all the lesser known titles Nintendo showed at E3 (Monado, Span Masher, Line Attack Heroes, Endless Ocean 2) Sin and Punishment 2 is the most popular of the bunch. Not to mention Reggie said a few weeks ago he'd like to give Sin and Punishment 2 a good advertising campaign, so I get the feeling NOA is going to make it their flagship title for Q2.
And before anyone mentions Mario Galaxy 2, I honestly doubt it'll come out in Q2, hell I'd be surprised if it comes out during Q3. Unless Zelda Wii actually gets announced for a fall 2010 release, I fully expect Nintendo to make Galaxy 2 their holiday 2010 flagship title.
Unless of course, Nintendo actually feels that Metroid: Other M could carry the holiday season. The best selling Metroid to date is the first Prime which came close to 3 million but not quite. Mario Galaxy 1 has sold over 8 million copies. Yeah, I don't see them making Other M the holiday title over Galaxy 2. Unless of course Zelda Wii actually does come out in 2010.