I don't think its unlikely - Putin has hollowed out the system so much that there isn't an obvious institutional rival to him, nor is there a plausible base for one to emerge.
If (and it is a big if at this point) at least some of the regular Army are sympathising with Prizoghin, then its hard to see anyone who could get into a position to take over from him if he gets to Moscow and removes Putin. The crisis will come when he has to consider whether to keep the SMO going or not (as it did in 1917); I think he'd call it off and blame the previous regime for its incompetence / corruption because there would be so many rewards for doing so, domestically and in terms of foreign support.
I mean, I have no doubt whatsoever that if he did end the SMO with some kind of deal he could accept (say Crimea is recognized as Russian and sanctions lifted, withdrawal from all other parts of Ukraine) then we in the West would grab that with both arms.