> Are they phasing out their own Bada and want to keep their options open?
It seems to be the case, with some people saying that Bada will disappear in the coming year as a separate option, to be folded into Tizen (so there will be a migration path for Bada applications). At this stage it's just hearsay, will have to see.
Interestingly, there's also been rumors that HTC, Acer and Asus are also planning Tizen devices too. It looks like Android players want another option, and WP is not seen as one anymore. From a support point of view, I would guess that supporting a linux based Tizen device is much simpler when you already do Android that a completely different OS (which is still Qualcomm only) like WP.
But things change fast in mobile devices, so we'll have to see what comes out of this in the end.