With Barcelone's current squad and style of play, I think Sergio Busquets is much more suited to them than Yaya Touré and I don't think they regret that decision. Of course, Touré has been really here but I don't think he would have done the great things Busquets has done in the past few seasons in Spain, so no worries about them wanting to sign Touré back: if they want someone to rest Busquets, they have Chelsea's Romeu and their own la Masia young players. And let's not forget about Mascherano who also is one of the better DM in the world.
In that perspective, only way I can see them signing Martinez is because they want someone polyvalent who can also play the defensive role like Mascherano, but that would be in the case they don't get someone they really want, ie Thiago Silva for example.