He has too much value to be a back-up. It would be better to trade him because he's worth more in a trade as part of a package then he is being #2 to Ramos.
Not to be too cynical, but I could see a year (2012) in AAA (or starting this year in Harrisburg), which will be Ramos's 2d year full time in the majors. Maybe a call up, maybe not, in September because he's on the 40 man roster. Then another year (2013) in AAA, which will be Ramos's 3d in the majors and last pre-arb. Then Norris up as a backup the next year (2014), making MLB minimum, as Ramos starts getting expensive. Sometime in Ramos's 2d year of arb (2015), with one more round before free agency, and Norris making MLB minimum, you then make the decision.
I could easily see this play out, but I do think the more likely course is Norris is traded before 2015.