Could global warming make Antarctica habitable?

Not in a meaningful timeframe, I think. Even if we get a worst case outcome (say +5°C by 2100, ongoing warming), permanent land ice in Antarctica will likely take many hundreds, or even thousands of years to melt entirely.
It's always going to have frozen winters with lots of snow, due to the long dark polar winter.. I guess some boreal tundra species could survive that, but farming is probably unlikely to be viable, I would guess.

Yes, while simultaneously making huge swaths of the rest of the world uninhabitable.
- plus, the archipelago under the ice is likely smaller then the land we will loose from rising sea levels.
  
  As long as we evolve gills and start drinking our own piss we should be fine.

Besides temperature there's the issue of sunlight.
We'd need plants for agriculture adapted to a completely new life cycle.

In short, no. Not at least outside of a vast geological timeframe. Antarctica was once habitable around 100 million years ago, and that was only because it was part of a supercontinent located much further north than its current location.
Even if the earth warmed enough to melt the ice at the poles, its location would basically make it impossible to maintain a complex ecology suitable to life. The light cycle of roughly 24 hours of light in the summer and 24 hours of darkness in the winter would preclude the needed agriculture requirements needed to sustain any meaningful population.