No, it wouldn't. People watch college basketball because the sport is fun to watch and to root for the name on the front of the jersey's, not the name on the back. 5-15 kids per year going to play for a year in Europe instead of college would have 0 impact on the NCAA.
If the players don't like how the NBA is run, they should start their own league, own the teams, own the capital, and set the rules. Won't happen. You know why? Because it's the capital that makes the league work, not the players.
If some crazy alien race were to land on earth today and kidnap every rostered NBA player on the planet and then disappear with them all, never to be seen again, the NBA would refill it's rosters and resume operations within a month. In a year, hardly anyone would know the difference. Yes, elite players are special, gifted, uniquely talented, etc. They are not irreplaceable.
Obviously, I know this is not a popular opinion, but it's the truth. The music world cries when a Kurt Cobain, John Lennon, Jimmy Hendrix, Janis Joplin, Jim Morrison, etc passes too soon. Music doesn't cease to exist or be made, the world goes on.