Six miles and a whole river apart. The Potomac River does seem to keep a lot of crime in DC and MD. Alexandria is a tiny city which would make parking atrocious (that’s the case now the Capital One arena so that wouldn’t change) but it is still serviced by the metro.
IMO they’re not going to move. This was a power play (pun intended) by monumental sports to force DC government to fund 600 million dollars of improvements to the Capital One Arena.