If DIRECTV doesn't widely feature it, it must be dead?PIP is a old outdated somewhat feature, most TV's don't even have PIP anymore.
PIP is in no way outdated. With the number of channels that are available today, PIP is as important as ever. That TV's can't as easily generate their own signals (not being truly "cable ready" absent some manner of built-in decrypter) for PIP has made it a lot harder to implement, but not less important. If DIRECTV made it available in more situations, I bet you would see much more interest in PIP than 3D.
Many Smart TVs support PIP in one form or another. I think most of the Samsung Smart TVs support PIP.