Based on your description and your location I think you can wait another month without any issues. By then it will be springtime and in my opinion the best time to up pot. If you really just had to do it right now it would probably be just fine too.

I have never thought twice about up potting a plant with inflos with the exception of any physical damaged incurred to the branches while sliding the container off the root ball on large plants.

I feel pretty confident up-potting at any time as long as I don't damage the roots.

I've seen videos on youtube where the plumeria have all the dirt shaken out of the roots and the roots pruned back before repotting. Is this correct? I've never done that to a plant before!

Root pruning can be done but not typically needed for a young plant which is being moved to a larger container. I save root pruning for soil changes where the mature plant has been in the same container for 3-5 years or more.

I agree with the above posters.. potting up will not cause issues with inflos, but I would not root prune any tree with a developing inflo.

K mentioned about having a more mature tree ( root bound) being 3-5 years.. That's usually the time we do this. It doesn't sound like yours need this, but just a potting up to a larger container. Just be careful and try and not damage the rootball when doing so. You should not have any problems!

Good luck!!

Laura