I doubt they will be releasing any 8.1 phones at MWC, but I think it is likely they will demo one. You would think Nokia would get the prototype OS early, being they are owned by MS.
Besides, we might have been "sorely disappointed", if the 929 came out on November 6th, and we had been putting off buying it based on rumors. Since, the 929 has still not been released ... we are missing out on nothing. For me at least, there will be no disappointment, and be a month closer to the 1820!!!
As for Windows 8.1 ... if the 929 comes out shortly, it will not have 8.1. I have read it will be compatible, but knowing Verizon and their extremely slow updates, Windows 8.1 phones will be available long before the 929 has it. I can see the thread already in the 929 forum, 'WHEN ARE WE GOING TO GET 8.1?", with numerous rumored release dates that are missed. :winktongue: