You could up-pot to 5 gal.sized pots and that might give a little better yield (that really depends on several things).
But the main reason I'm responding to this thread is to say that "Rootbound is really a state of mind". When you pull the plant out of the pot it's in, you can see what condition the roots are in. If "a lot" of roots are exposed and "twisting around" the dirt ball - that's not rootbound, that's just a healthy root system (perhaps ready to up-pot)! If it looks like a huge ball of twine with the roots all wrapped around themselves (so you can't see the dirt for the roots!), that's rootbound, baby! A true rootbound condition can indeed inhibite plant growth and therefore restrict the yield. But, you can also just deal with it, make sure you give it plenty of water and nutes!
Your grow seems to be in between "I could get away without up-potting" and "I should really up-pot, to avoid a rootbound situation". My advice would be to go for it and not up-pot, just for the experience you will gain! Whatever you decide to do - it's all about the experience!