I agree as well that this team isn't a playoff team next season with the same group. I don't think they'll be this bad, though a lot of things have to go right for this team to win 90 games.
This offseason, the team needs to add an impact starting pitcher. I'm sure Garza is out of their price range and I doubt a veteran like Kuroda would come and pitch in Toronto. I'd focus on bringing in someone like a Tim Lincecum or Ubaldo Jimenez - both have had solid years and should be durable enough to give the Jays 200 quality innings. They likely won't require a 5 or 6 year deal worth $90 million like Garza might demand. However with a thin market, Ubaldo or Timmy might get more than anticipated. The Jays also need to bring in a solid catcher, which should be at the top of the list.
This team is really only built for 2014-2015, so they only have a two year window to contend since they still have all their main guys like EE, Bautista, Reyes etc all under contract and they should still all provide value over the next year or two until they start to significantly decline. After that, this team is in deep trouble like you said.