To be honest I find it destressing to some extent that this is even a question, but since it's been asked I'll answer it with a resounding no. I do not think the WNBA should lower the rim and, even if they did, I'm not sure that this would increase the popularity if the league.
There are several reasons that it would be a mistake to make the rim lower for women's / girl's basketball than it is for men's / boy's. First of all there is no evidence that this would make the product more enticing. I assume this proposal is rooted in the idea that access to slam dunks and increased shooting percentages would improve the game.