Well, this is pure speculation, but I suspect a bit of both. He may be a neocon in DC, but in the end, he's a very nationalist Pole, whose views are determined by what he believes to be Poland's national interests. Plus there's his horrible relations with the twins - i.e. domestic political considerations. I get the impression that during his stint as Defense Minister he grew a bit disenchanted with the neocon line. He's since been purging the Foreign Ministry of some of the radical right wingers and PiS hacks that the twins installed after pushing out Stefan Meller, their first FM who was a longtime senior diplomat and part of the left-liberal camp which has dominated the ministry since 1989. Sikorski's appointments have tended to be a return to the status-quo ante.