I think Alaap and Niharika will surely come to know the raaz. If not Niharika atleast Alaap will get to the truth.
Here are a few possibilities:
Suyesha may find the tape, listen to it and fight with Alaap about it at Michi's wedding. Suki's marriage will immediately break.
Or
She may find it and fight with Alaap alone who will give some excuse to shut her up. Then he may use this to blackmail Milsi into giving him the SM.
Or
Niharika will get to the truth and blackmail Milsi for more money and it will be a never ending trauma for Milsi for this lady will never be satisfied.
Or
Ayesha will get to the tape and pass it on to Niharika to take revenge against Suki for spoiling ehr chances with Milsi
Or
She may be talking to herself about how everything was ruined because Suki is the mother of Ritwki and not Prachi and Neev overhears it but does not tell Saket for he does not want to hurt him. He will however take revenge against Milsi by bringing his business down and Milsi will let him do it.
Any other possibilities?