It does appear that it is Tendulkar's prerogative to continue .
Observe, for about 2 years now, how conveniently he becomes UNFIT and then becomes FIT as per his own declaration. BCCI doesn not have guts to ask him to get clearance from Physiotherapist etc., as required by other players.
He will not retire ON HIS OWN Selectors do not have guts to DROP HIM. So there is actually no way out.