I am worried about this too. With news of the Mclaren device being cancelled, and no word on ANY high end windows phone coming to AT&T (with the rumors of the 830 mid range windows phone) I dont know what I will do. I know there are millions of lumia 920's coming up on the contract renewal at the end of the year. So.... With that being about 15% of thet total windows phone users, and being on AT&T's network because of exclusivity there might be a mass exodous to other platforms or other carriers. I personally have three devices (all windows phone) on the network, two of the three are up for renewal between now and the end of the year. I am afraid that if there is no upgrade path for me within AT&T I will have to move over to Verizon who is getting all the new devices. I am loyal to the platform, not the carrier, althogh I have been an AT&T customer for near 15 years.
That is my situation too, my 920 is up this fall. I'm stalling my wife's upgrade and really don't want to move to Verizon. Cross our fingers that MS has some surprises. There has been hints LG might get in WP.