We're surely going to sign a classy CB sometime soon, but not now.
Soon we will need a world class CB (not a back-up), because Puyol is starting to get old, we could say the same about Abidal and I'm not sure what's really going to happen with Masch in a perspective (is he a CB, is he a DM, will he stay in long term?)
I guess in 2012 or 2013 Barcelona is going to hunt the market for a classy, solid and surely more expensive CB, so Thiago Silva could be option for us again. It seems that Pep rates him highly (remember he was one of the Milan players we wanted during the Ibra talks), so especially if Pep stays, Thiago will be a target I guess.