I don't think Nintendo would be against Sega in this. I believe some Nintendo figures have said that this service isn't motivated by profit. Of course, they're going to make money off of it, and they're going to try to milk it (it's Nintendo!), but I'm pretty sure they're not worried of losing money to Sega. Really, I think the idea for this service came as a result of their position; they can't compete with Microsoft and Sony who'll try to outdo each other with their money. So they asked themselves, what can we have, that they can't? Classics is the answer, and if they lose Sega/other classics to other systems, then this service is of little benefit to them.