Do you know what kind of hibiscus it is?
As long as there's a good root systyems growing, I would got ahead and pot it up with good, well draining potting soil, water it well and keep it warm. Make sure the pot's not too big - if it is, the soil will say wet and could cause root rot.
When spring comes, you'll need to know the species to know how to deal with it.
Barb

Thanks for the info. I think it's a Hibiscus syriacus.

If it is, then it will be hardy in the ground for you in Tennessee.