Putting Lavarnway on the ML roster this year any time before call-ups does not make a whole lot of sense. He would not get enough of the experience he needs at this point, especially on defense. Presumably, he would play mostly, if not exclusively, against lefties. He has to bat against righties in order to develop as a hitter -- and to show prospective suitors in a trade that he can handle righty breaking stuff. OTOH, in AAA, he is getting experience and is being showcased every day. He doesn't see ML pitching in AAA, true; but he sees enough pretty good pitching, lefty and righty, for scouts to get a good idea of his potential as a ML hitter. I know that a lot of people think that question has already been settled, based on Lavarnway's short stint in Boston last year, his college career, and his previous MiL experience. But scouts will keep checking. They always do, regardless of a player's previous record. That is doubly the case if the team represented by the scout figures to be asked for a player(s) of marked value in return for Lavarnway. The way these things go, he may be more on trial behind the plate but he's still somewhat on trial at the plate.
If Boston brings Ortiz back in 2013, even for only one year, Lavarnway with the Sox is essentially a back-up catcher. Unless Salty slips badly or is traded. IMO, the odds are against both. OTOH, if Boston lets Ortiz walk, there might be a spot for Lavarnway as DH and reserve catcher. Hard to say whether Lavarnway, at his age, would be content with that arrangement.  My guess is that most players his age would rather be in the action -- unless they are manifestly incompetent in the field and are told that they are lucky to the playing in the majors at all -- at DH. 
We can be sure that all these considerations are being mulled in the Boston FO, especially if they are chewing on the possibility of offering Salty a long-term contract, not tomorrow maybe but in the off-season if Salty has a very impressive year. 
What all of this boils down to, IMO, is that Lavarnway's future in Boston is tied up with Salty and Ortiz as much as, if not more so, as how he performs. 
It will all play out in time, as these things do, probably sooner than later.