Sounds like the shop you took it to is flat on their arse. I have a 2006 Yamaha F250 and my lower unit went out. Bill Marine in Portsmouth had me up and running in a week, a brand new lower unit paid for 100% by Yamaha warranty. I'd find it hard to believe that Yamaha has been sitting on your warranty claim since June, a more believable explanation is the shop you took it to didn't take care of you and sat on it this long.
But glad you will be back up soon.
Mike
Hydrasport 2900VX
Seaduction MMSI 338-018-823