It doesn't seem that AT&T knows what to do with DTVN, and even if it did, it would still probably screw things up like it does with everything it touches.
However, I suspect many of the original grandfathered subscribers are still hanging on, because the fact of the matter is that as long as those packages are still offered, they are still the best value in a market that has seen prices rise for everyone.
I'd have no regrets about kicking DTVN to the curb, but after doing some comparison shopping, I'd end up paying more, for less, even if I can accept some compromises. The real kicker, and not up for compromise is HBO, which would cost 2-4x what it costs on DTVN. AT&T needed to grab Time Warner, like every other dumb-pipe company that wants to compete in the future, and for now, that vertical relationship is still favorable for consumers.
Until AT&T cuts off the grandfathered plans, and forces everyone's hand, some will still remain onboard. But I have no doubt that it's a "when," not "if," that will occur.