Really that is up to you. If you just out and out decided to dispense with repotting entirely, the plant would simply -- one day -- completely envelop the pot. At that point you could simply grow it as a hanging plant much like a vanda.
However, assuming you would prefer to continue growing it with the majority of roots inside a pot then I, personally, would recommend waiting until this flower spike is finished -- but then I tend to be rather clumsy and could easily foresee myself accidently snapping the spike off during a repot. No need to wait until next spring. The spring "rule" is really more of a suggested guideline ... not written in stone.
Do make sure, when you go to repot, that you soak the potted area for a time to soften up the roots and to make it easier to separate them from the terra cotta pot.