What if when they come out with the next system then they will let you have two since its rumored the next one might be headless? Maybe the next guide will do both SatelliteTV and IPTV and then the new system could connect to old one?
In my opinion, while you're headed down the right path, I don't believe that AT&T is going to require anyone to have any more than one Genie DVR on their account at any given time. Why is this? Because of OTT (Over the Top) streaming. Such streaming plans (as they'll eventually arrive later this year and going into next) do not require the same physical architecture and topology as what's required for a Genie. With streaming, the only practical limits include the end-point devices as well as any legal content restrictions there would be on programming.
In such a scenario, the Genie DVR would remain as the main physical box for local storage (I'm going to assume that AT&T won't need to provide cloud storage, given that an account with full programming access would already have a DVR) as well as the main viewing device when not on a mobile device. This would make the most practical sense and cause the least disruption in getting folks from one type of viewing to the next (my pre-teen kids already consume 75% of their video over mobile devices of one form or another).
Granted, I could be full of hot air, as I have no special access to any plans, just a background in tech. Besides, the above would leave AT&T with no more sunk cost investment than they already have (except for whatever would be required to stream) and would be the least disruptive to consumers, and such a transition to the devices consumers already have also makes sense (see also: iOS AT&T app streams video without impacting AT&T wireless data caps).