I think Nintendo would overlook any possible xenophobia they might have about a non-Japanese developer, if that developer was vehemently supporting their console and helping add interest in it, something I think Ubisoft is doing more than any other 3rd party right now. It usually comes down to sales and support, both of which Ubisoft is helping contribute to the Wii U. Nowadays Nintendo knows that non-Japanese developers are very important for the system's "hardcore" success, and I doubt they would discriminate against something that helps sell their own product.The main issue with Rayman is that he's not created by a Japanese company. Not to start up any racist controversies, but generally Japanese companies have a distaste for other companies from other countries (USA in particular). Not sure if Sakurai and his rag tag team of developers follow the stereotype, but its possible we'll never see Rayman. Especially considering that Rayman is pretty obscure in Japan.
A shame too, because he can easily have a moveset and fit in the crowd as another quirky character. Plus being a limbless character would make him stand out from the other characters barring possibly Sukapon.
I think the point that Rayman isn't overly popular in Japan and isn't really requested heavily anywhere would be the main reasons he wouldn't get in (more so than pro-Japanese sentiment that Nintendo might harbor). However, if Rayman hypothetically was requested as much or more than Megaman in Japan, I don't think Sakurai would dismiss something that would help bring sales in just on the fact that it's made by a French company. Since he's not though, I would agree that there is a very good chance we'll never see Rayman in Smash.