Perhaps SWISS will help to open up parts of central and eastern Europe.
However, I think that OneWorld should be looking seriously for an Eastern European carrier. Star poached LOT right of the vine (and LOT is probably the best run of the Eastern European lot). Skyteam already have Malev (I think?). So it leaves precious little for OneWorld. Given all those countries are about to join in the EU, it could be a good investment.
One way around it may well be convincing Finnair to project into more parts of Eastern Europe.
The other obvious gap for OneWorld is China, although CX's expansion may fill this gap over the next few years, as well as the talked about QF service to a port in China.
A smaller gap in OneWorld is Canada as AA services there aren't that great.