A#1 location is Seattle.   If expansion happens, it is almost certain that Seattle will be accepted for a team.

2d team:  Less certain here.      You could go with teams in cities that already have big league teams, but no NBA:  Baltimore/Pittsburgh/Buffalo/Cincinnati/Jacksonville/Nashville/ Kansas City/St. Louis/Columbus/San Diego/Las Vegas

Or, you could do what the NBA likes to do:    Put a team in a market where there are no other major teams...i.e.  choose a town that would become a one horse town. There I see the following as the only real potentials:

The Tidewater:   Va. Beach/Norfolk      It is THE largest Metropolitan area in the USA without a team in the 4 mains sports:

Greensboro  NC (including Winston-Salem...Raleigh Durham which does have hockey

Louisville

Hartford.   

the other possibility would be to put another team in Canada:   Montreal....or one of the western cities. 

My preference:    Virginia.