Question related to H1B transfer

What if my H-1B transfer is approved with a new employer and I decide to stay with my current employer? Do my current employers have to re transfer by H1B back?

No. Current employer do not need to do anything. Your new employer will withdraw the H1B once they know you are not joining. The change of employer (aka transfer) do not happen until you leave the current employer and start working for the new employer.