I think this would be a cool idea, more like the MMOs on PC, just getting a huge expansion that is actually worth paying for every few years. For example SWTOR is about to launch their expansion on Dec 9, for $20 they are adding in a ton of end game content and 2 whole new planets in addition to raising the level cap. I would rather see Destiny have this kind of model but for some reason I don't see that happening.