I had 2 sessions of Brazilian laser hair removal and now I regret it, the hair is almost all gone. Would the hair grow back?

Industry Standard recommends 6 treatments done 2 plus months apart. Since you are 2 treatments into the process it may have just thinned it out and therefore you may get a great result. Give it time for the remaining cycles of hair to grow in. You can even continue with a partial bikini and only treat the hair in the areas effected when wearing a swimsuit.

We would suggest giving it a little time to determine if the hair growth cycle will cycle back around and possibly lend to a different outcome.  Unfortunately, you received two good treatments (good if you wanted the hair removed), with an end goal of permanent hair reduction.  If you are noticeably patchy, then it may be worthwhile considering options to regrow hair...which is a bit more challenging.  

I recommend getting a formal evaluation with a hair loss expert. Prp and progesterone can be used to regrow hair. See an expert. Best, Dr. Emer

A large percentage of the hair will grow back however, the area may have some thinning since not all of the hair follicles were in the growth phase at the time of your two treatments.

Much will depend on how effectively your first two laser treatments were.  Assuming they were at an appropriate fluence and that the treatments were performed about 2-4 months apart, you should have decreased you overall dark hair density by about 60-70%.  Typically 3-4 well performed treatments, will reduce the dark hair by more than 90% and the 10% that remain (assuming they had been treated but returned) will be finer than typical pubic hair.  If you don't do anything for at least 6months, you should be able to see how much hair actually is left.  It may be patchy at first but may even out a bit over time as the phases of hair growth flow into each other.  If you don't like how that looks you may want to complete your treatments.  Hope this helps a bit.