I pm'd the nvidia guy in that thread, requesting an up date and he reached out to rockstar and got an update:

Quick update on this:

We checked in with Rockstar again as these should have been back by now. They've been working through December to get them back up. They don't have an ETA yet for when they'll be ready but they've promised they are coming back.

I didn't even know they were gone. I purchased San Andreas a while back, but I just have it installed on my computer now.

Huh. Earlier this week I pulled the San Andreas app from my phone and installed it on my MiBox. Outside of the launcher icon you'd never know it wasn't meant for it. Cranked up the settings and everything. Guess I'll know they've made it native when the app updates.