Habitability of Titan in a few billion years, and how to explore it now

An article here from the Guardian includes a bit on what Titan may be like in a few billion years after the Sun has swelled into a red giant and swallowed the Earth. Titan right now has an average surface temperature of -180, but by that time it should "heat up nicely" and along with the presence of an atmosphere and tons and tons of hydrocarbons it may become a nice destination for life.

The actual size of the Sun by that time is expected to be about 2 AU in diameter, so just large enough to swallow up the Earth. From the orbit of Saturn then it should go from this:


to this:

It goes without saying that Titan is the most interesting moon in the Solar System (except perhaps Europa), so it would be nice to have a mission sent there to fly around and observe it over the long term instead of just flybys from above. A nice practice mission could be a proposed solar flyer or balloon-mounted probe on Venus, as this is fairly easy and cheap to do, and could provide a lot of data and training on how to properly manage a mission of this type on another body, plus it would demonstrate the concept for the first time since the 1980s when the Soviets sent balloons to Venus. At the moment probes consist entirely of two types: those that orbit a body, and those that land on the surface and begin crawling around. Venus and Titan though are the easiest destinations to fly over in the entire Solar System. Titan has much less solar energy than Venus, but the gravity is also minuscule in comparison (just 16% that of Venus).

Wikipedia has a nice image here showing the atmospheric pressure vs. altitude on Titan.