If Brown, Tatum, and the Lakers/Kings pick develop into all stars, that's a potential core for the next 10-12 seasons. In the meantime, if Ainge can surround this core of Irving, Hayward, Horford with enough talent while the youngsters develop then, yes, this team could contend for the next decade.
Lots of things can go wrong but I' excited about watching this team for a while.