There's little chance of that, I'm afraid, for the simple reason that while Wenger Himself may merely wish to stay, our board is absolutely desperate for Him to stay. I mean, if they were to ask Him to leave, He would leave, whereas if He told them He wanted to leave, they would beg Him to stay.
So, in a sense, He's got them over a barrel, albeit a mutually agreeable barrel. And an attempt to insert any such ejector-seat caveat or clause would simply be rejected by Wenger's people. Therefore there would be no such attempt.
After all, we didn't offer Him a contract extension because we wanted to sack Him, did we. We did so because we (or anyway, E. Stanley & Co.) want Him to stay.