No, not too late for 8a. Even if it was, it would be fine since you're bringing it inside.
If its root bound, or close to it, lightly hit the sides of the pot with the bottom section of your palm, turn the plant in the pot upside down while holding your hand over the pstem base/soil so the plant doesn't fall out onto the ground, carefully slide the pot off the root ball (root ball will be in the shape of the 3 gal pot), and put it in a larger pot with more potting soil mix. You wont mess up one root and will have zero transplant stress.
I prefer no larger than a 5 gallon pot if you're expecting to plant it in the ground next spring. When I plant from pots in the spring, there is zero stress or stall in growth because the root ball is in the perfect shape of the 5 gallon pot. Any larger than a 5 gallon would be messy and could cause root damage when you plant into the ground, if that's your plan