Womens sports have (rightly) gotten away from the "Lady Celtics" type names (old enough to remember when college teams were sometimes referred to that way). They don't call the womens soccer teams in Europe like the Ladies of Liverpool, do they?
But, yes, if there were a WNBA team in Boston that was also called the Celtics, it would probably benefit from a built-in natural fanbase (not to mention marketing and facilities and such).
That said, the relationship between the NBA and the WNBA has kind of been a saga. About half the WNBA teams share ownership with NBA teams, not everyone thinks that's a great model. I dunno.
One WNBA owner tells Front Office Sports that independent team ownership is what's best for the league long term.
frontofficesports.com