Yes. Though it may delay the release of the full game, it can allow 343 Industries to experiment with some of their ideas and get feedback from them, good or bad. If the feedback is good, keep it intact in the full game. If it is bad, take it out. It allows people to get a taste of the game early as well, and the game would be thoroughly tested for glitches. A Beta is just what 343 Industries need to make in order to make the possibility for Halo 5 being the best Halo game significantly larger. Halo 3 had a beta, and look how well that game turned out.