You can wait, if you want, it'll be awhile before you'll habve to worry about them becoming rootbound, if that was your concern. They'll grow faster if you transplant though, as the roots spread and fill out the larger pot, so it's be a good idea to do it when you get time. The plants will also get bushier, as the roots grow outwards. Just look at a party cup grow, and you'll see what I mean. They are always tall and narrow,(unless trained) because the roots are confined.