i still see it that way, too, tam. in wenger's mind, he's got 3 top CB's (djourou, vermaelen, koscielny) and the #4 slot will be reserved for bartley next season or the season after. squillaci is just a placeholder so the team doesn't fall apart in the event of injury.
wenger's not going to buy another top class CB. he's going to look for another squillaci/silvestre/campbell, ie another short-term placeholder.
i still think we might be better off buying a good DM. i don't rate song as a CB, but as 5th choice, i think he's of reasonable quality and keeps the team from falling apart, which is all another squillaci/silvestre/campbell signing would do. plus, we actually have a need at DM, since i'm not convinced that frimpong, coquelin or eastmond will be legitimate replacements for denilson next season (though i hope one of them will).