I think it's safe to assume that we'll have bigger and better than Halo ever was, so lets try not compare it.
As for lore to stretch, I can't even grasp how Bungie even built up something so gargantuan for Halo; so I'm having difficulty seeing how they can equal it with Destiny when it's not going to link to Halo like some of Bungie's other games, and also, the have told us absolutely squat about Destiny or any of it's backstory.