I'm planning on riding WMC out until it's no longer possible on my main TV. I haven't tried exploring future options yet due to not having any time...
My main use for it is for DVR purposes along with my HD HR prime
I switched over to OpenELEC, and havent looked back. The only real issue is my HDHomerun is not supported by the HDHomerun add on. I have to figure that out before football starts, but since I have the NFL online package I guess it doesnt matter that much. I was actually surprised how well everything worked. I think I only had to use a shell once, and that was to set a custom skip forward/back interval. And surround sound now works! I must have changed something when it was WMC and forgot about it, and just got used to stereo when using WMC. And when I used Plex on my FireTV AC3/DTS is downmixed. Kinda feels like I bought a new sound system.
Come to think of it, all the things I used to use the FireTV for I now use the OpenELEC box, except Prime Instant Video. I use the htpc more with OpenELEC than I did with WMC. WMC will not be missed.