This question is seriously getting annoying. This is Verizon's variant of the Lumia 1520. Seeing as how it is a variant, it is HIGHLY unlikely that this will come to any carrier except Verizon.
That's your
speculation -- there's been no official announcement of any kind. However, experience has shown us that the "carrier variants" differ in fairly minor ways (shape, memory, wireless charging, and LCD/OLED tech).
I don't think that any carrier variant has ever varied in screen size.Since the 929 is supposed to be a 5" device and the 1520 is a 6" device, it seems to me like these are different models, not carrier variants of the same model. It's reasonable to guess/hope that AT&T and/or T-Mobile will get a 5" device and that Verizon will get a 6" device, should those carriers want to offer such a device to their customers.
The OP is asking is there are any rumors or leaks that point to a 5" WP device for AT&T. As of now, I believe that there is no such information. Even if they were planning on offering it, they would be wise to keep it quiet so as not to diminish potential sales of the 1520. Still, so far there's nothing.
On the bright side, if you can live with HSPA+ speeds (instead of the latest and greatest LTE speeds), the 929 is supposed to be SIM unlocked and I believe is supposed to have the HSPA+ frequencies that AT&T uses. This might work for your needs. One thing that we can't yet even speculate on is whether or not tethering on the AT&T network would work with such a device. My guess is that it would not, but that's my speculation.