The way RK stopped Madhu from going near the phone was quite significant. Although RK was heart broken, any other ordinary person in that situation wud have hated to hear his enemy and would have probably banged the phone on the wall, but then RK is no ordinary mortal , he wanted to hear exactly what his new found Gangu Bhai wanted to say. Gangu Bhai assuming its only for RK's ears, gloated away and in his hate for RK let his carefully guarded secret on Madhu out. Which has not gone unnoticed to Madhu, So Madhu finally gets to hear the real side of her Golden Hearted Friend.
RK, once he settles down after the shock, will be back to the old scheming and devious RK. RK has carefully listened to each word of Gangu Bhai's sermon. Knowing RK, he will never regret whatever he has said or done to Gangu Bhai. At that point his regret was only with his father not his own actions, as RK never had any pretentions to being Golden Hearted or ever being one in future. So we can definitely expect RK to repay Gangu Bhai with DOUBLE or TRIPLE INTEREST each of Gangu Bhai's taunts.
So lets wait for RK to come back to his normal self with lots of help from Madhu. Infact the bright spot in this entire breakdown of RK, was that the couple has become closer than before, Madhu has become more protective and loving towards RK . So we can see the couple tiding the crisis in unison.