It's good for both the UFC and Ronda...MMA has less to do with it. It's on the UFC to produce cards which retain the fans who are tuning in to see Ronda. By adding the women's divisions and giving talent a chance to grow, they're doing just that.
Will some people become disinterested if she isn't fighting? Of course-- that's part of the game. How many Irish fans suddenly took interest in MMA, when McGregor became a name? Conversely, how many Irish fans fly to Vegas for cards not headed by McGregor? Are we worried about Irish fan retention for non-Ireland cards, or once he exits? How many Canadian fans continue to watch Lawler fight? How many have stopped caring about MMA since GSP retired?
These are the questions nobody really cares about, and neither should we care when it comes to Ronda.
If her fans no longer care to watch MMA, that's on them. The hardcore fanbase won't change and the product will continue to adapt, as it always has. Any business which can't adjust to ups and downs, or spikes in appeal, will be doomed to fail. The UFC has shown that they can, and already have a diverse enough product in many ways.
Also, the UFC (and its hardcore fans, especially) are a company/group which has always lived in the moment. Their approach can be described as "what have you done for me, lately?". The simple fact is, when you have something good, you milk it, until it's no longer good. The money and exposure she brings to the UFC, now, is very real. The money she pockets is very real. What happens after that is not her concern, while the UFC will simply contract and push their next big star.