if Virgin see a value in handing over slots to Flybe, it says a lot about the profitable use of shots for their existing long haul network, I would imagine a slot would be better utilised to a north American destination...
Wonder longer term will the slots revert to long-haul. Perhaps aircraft shortage with DL / VS is the reason.
Should A220 become a reality, could see these on the LCY that seems to be performing well. I know a few separate people that fly to London weekly, and have swapped from BA Heathrow to BE City, esp as can continue to collect Avios.