I don't see their motivation for this. They are already making successful phones with Android, what would making their own OS accomplish? That would take a bit of an investment just to develop and test the software, and then they would be pushing another OS into an already crowded market with no apps to it's name. With each new OS, the amount of developers willing to work on them gets stretched thinner and thinner.
If it's something they want to dabble in while still making phones with Android and Windows Mobile, I can understand that. But dumping those for something new makes little sense.
I hope they stick with Android.