Let it go in that pot for a while longer, at least until its just a bit taller than the pot. When you do decide to transplant, transplant into the plant's final container size. Less transplants, less stress, happier plants. How often are you watering? Make sure not to over water, the plant looks a tad bit droopy.
I would wait another 1-2 weeks before transplanting. It is still young. Looks good though! Patience my friend.
Wait at least 2 weeks and let it get real dry when you transplant. Dry root balls slide right out real good.