Few things here...
First, Super Paper Mario in April. Great news, now I have something new to play for Q2. If only I didn't have to use my leftover 2006 vacation time before April. ::Sigh::
Mario Party 8 was actually just delayed into Q2 (source: Game|Life), so it won't be making March anymore (your guess is as good as mine).
I wouldn't expect Super Mario Galaxy before August, but I'd love to be proven wrong. I expect Pokemon Battle Revolution will be Nintendo's big June title to follow up on April's stateside releases of Diamond and Pearl for DS. With all the kiddies getting out of school and Wiis (presumably) readily available to purchase by then, it makes an awful lot of sense.
For SSBB, I expect Nintendo's usual Monday before Thanksgiving ship date.
Finally, Mario Kart 64 is Virtual Console next Monday and Nintendo has not announced a new Mario Kart for Wii as of yet. Personally, I'm kind of curious if the two Namco arcade versions will ever be brought home, though I have no idea if they're any good or not.