They don't need transplanting
right now, but they will in a week or two, depending on how quickly they grow. I meant you should start planning what you're going to do when they get bigger, buying larger pots/more soil, etc.
It's been a while so I can't remember if these are bagseed--I
think they were. Even if it's a breed that grows "small" you're still looking at them being 2 feet or so before they reach flowering (after which they'll grow even more). Keeping them in a smaller pot will help keep the size down but if the pot is
too small, the plant will become
root bound and won't be able to absorb nutrients (a.k.a. nute lock-out). If you want them to grow to their full potential, they should move to at least
5 gallon pots.
Alternately, you could let them get to whatever size you want, and then force them to flower by bringing them inside and keeping them in pitch black darkness for 12 hours, then putting them back outside in the sun. But you'd have to do that every single night for the entire flowering period or risk your plants re-vegging or hermie-ing due to the stress. If you did that, you could keep them in smaller one, maybe 2 gallons, depending on how quickly you switch them to flower.
But then, I'm only on my first grow so maybe someone with more experience can give you better advice.