I somewhat agree with crando, but there are other worthwhile games on wii apart from mario galaxy (e.g. paper mario, mp3, re4, msc, bwii, mario kart, wii play, etc.) PLUS you have an endless list of classic games on VC like super mario world, mario 64, mario bros 1, 2, and 3, etc. etc.
IMO work out what games u like on wii and then decide whether it's worth keeping for the time being.
IMO this would be the worst time to sell your wii, because essentially the wii is at is peak (at least compared to the rest of the year). So keep it now for smg (that is if you like it), and after that decide whether to keep it for ssbb, mario kart, wii fit, etc.
If you don't like those games then sell it after smg, and get a 360/ps3.