As Robert pointed out, that 5 acres sits in the middle of very desirable Crown Estate property at the edge of Windsor Great Park. I would think any wealthy / aristocratic family (or Russian oligarch) would be very happy with that site as a home.
That said, the most likely scenario is that somebody will eventually buy the freehold, tear down the house and replace it with a new one. It's a rather uninspiring house anyway, not really worth restoring to its original condition (at least IMO).
My mind wanders to "what ifs". I would assume that after the QMs death, Andrew would have inherited Royal Lodge anyway (even if the York marriage had lasted), meaning Sunninghill Park would have still needed to be sold, or perhaps given to another royal family member. I wonder if it might have ended up as the Cambridge's country home, or perhaps Harry's eventually?
