If all quality 3rd party support leaped to the PS360 and it came down to only Nintendo and the shovelware makers then I would say not. If the Wii's library consists of 98% crap and 2% quality, odds are most average consumers will end up with a lot of crap and not be satisfied.
Also, it's not solely a factor of 3rd parties not supporting Nintendo rather 3rd parties supporting systems other than Nintendo.