Either way, I have mixed feelings about it. Somepony needs to be responsible for the ringed planet, after all. (Note: in the opening of Seasons 1 and 2 of MLP:FiM, where Celestia is shown in her throneroom with two guards, there is a window visible that depicts what I assume is the solar system the ponies live in. It has round planets, one of which has rings. I'm not sure if Equestria is a nation on the landmass visible on the earth-esque planet at the bottom of the window, or the landmass in it's entirety, or the planet in it's entirety, though. There's no way to judge scale for anything other than that landmass- Assuming an earth-sized planet, it appears to be roughly as large as North America, maybe Asia.)
So yeah, on the one hoof- er, hand, there's that ringed planet. There can be more Princesses that control other celestial bodies like that one. I wouldn't mind that at all, it'd make sense really.
On the other hand, so much fanon will be destroyed. I'm rather attached to some of it.
And on the third hand (...am I an octopus now?), there's always that fear of any major changes to what seems to be a working formula.