I don't really think there is any way, sorry. Bungie needs people to keep buying expansions, and it's only a matter of time before they create a few "ultimate" weapons that they can't top aside from just saying "But this one has higher numbers!!1!". They can't get people to buy DLC with the phrase "Don't worry, these weapons won't make your current ones obsolete because these are not actually better! In fact they're actually a little bit worse! Buy now!"