I'm pretty sure it's a completely new universe, so it would have to be more of a reference than an easter-egg. For example, the Marathon symbol was a reference in Halo, it didn't mean that both Marathon and Halo happened in the same universe. If there was a reference to Halo in Destiny, it would probably be with a certain symbol, in dialogue spoken by an NPC, or in the name of an object- perhaps a rocket launcher called SPNKR or a set of armor called MJOLNIR.