We have two providers in my city - Time Warner Cable & ATT. TWC's best internet is a paltry 50/5mbps and their TV is ridiculously overpriced. To TWC's credit, they have been slowing bonding more channels here (we're getting 6-8 downstream channels locked now), so speeds have crept up into the mid-to-upper-50s, but the price is just never the same month-to-month. U-Verse just started offering 45/6mbps internet here, so I'm going to give that a shot next week and see how it is. Hopefully it's better than when we had 24/3mbps a few years ago.
To the original question - I would seriously doubt the XB1 will act as a STB for U-Verse. ATT announced a few weeks ago that they were ending support for existing Xbox 360s as STB, so I'd imagine everyone will have to move over to their boxes. I've got a HDHomeRun Prime I use for cable with CableCard and Media Center now - I really wish ATT used cablecard too.
Ericsson bought Mediaroom, so perhaps they couldn't come to an agreement with ATT. There aren't many other IPTV platforms out there, however, so I'd imagine they'll be using Mediaroom for the foreseeable future.