I don't think Bayliss is going to replace Hayden. Ducati won't give up on Hayden that quickly, and as hard as Hayden works, it will only be a matter of time before he is moves up in the standings.
I think Troy will give imput and help develope the bike. What a cool retirement gig! Ride the most advanced bikes, help develope them, get paid good money to do it, and have none of the pressure to win championships. Perfect job if you ask me, though I know competition is in their blood.