It is expensive, but if you figure you get all three games with improved controls its worth it. Try adding up the price of Primes 1, 2, and 3. Prime 3 alone is probably $50 still. The only way it isn't worth it is if you already own one or two of the games, in which case it may make more sense to just buy whatever one you're missing as opposed to buying the Trilogy. But the nice thing about the Trilogy is the new controls and the nice metal collectors case. It is also nice to have all of them on one single disc. So whether its worth it or not is really up to you.
I wouldn't hold my breath on this being a Nintendo Select title. Nintendo may release the primes individually as Select titles for $20, but I doubt they are going to do it with the Trilogy because why would they give all three games away for $20 when they could milk them individually and make more money? It is possible, but I doubt it.