Is the reason its not planted out in the ground a space consideration? Just wondering with you being in Houston, it could be planted out.
You can unpot it like Christine said and separate them, you might have to use a pruning saw to remove the old one, but it usually does not affect the pup, this is the way banana plants are propagated all the time, by the corm being exposed and chopped up or a sword sucker pup being sliced off (with some roots) from the adult plant.
If you remove the old trunk and cut it into sections each with some roots and plant them, you may get new plants.
All my bananas are in the ground and we never bother to remove the old corms, but in a pot you will need to make space if you intend to keep it in there
