Leave it in a pot, or, even better, get a 2-3 gallon bucket and drill 1" holes around the sides (but NOT in the bottom!). Plant the vine in the bucket, then plant the bucket in the ground. This will allow the roots to grow out through the holes and get more water, etc., from the surrounding soil. Before your first frost, prune the top back to a manageable size, then cut around the outside of the bucket and lift for overwintering indoors.

I did this with mine for a couple of years, and it worked beautifully. I also planted a second one directly in the ground, and it did well the first year. But when it had to re-sprout the next spring, it didn't reach blooming size until a few days before frost.

I live in Zone 8a.

Thunbergia grandiflora---Blue Sky Vine---rarely ever makes seeds, and I hear they're difficult to germinate and slow to flower from seed. They're mostly propagated by cuttings.