It would probably be worth it to DL if they can gain even a couple of more Transcon slots for JFK/SFO-LAX plus the DAL gates, even if everything else had to be divested.
Plus it eliminates a competitor on SEA-LAX/SFO
So realistically even if DL bought VX, re-did the planes with DL livery and didn't keep any of slots besides the DAL gates I think DL would do it if the price was right. Plus DL has a strong relationship with RB already.