Perhaps, but at what cost? In Australia we got small hive beetle about fifteen years ago, and if we didn't have feral colonies these things would be much easier to manage. As it stands, feral colonies are breeding grounds for these and other pests and diseases, and also put our native bees at risk (by disease or competition).

I also have at least two beekeepers within 10km of me that are actively selecting and breeding up queens with very different priorities over characteristics, so I would expect that genetic diversity isn't at huge risk within the beekeeping / honeybee community.