User blog comment:Timeoin/Dragonborn Screenshots/@comment-4118072-20121120185400/@comment-3492791-20121120211140

They did not announce it. They have only released a date for Xbox but that does not mean it is exclusive to the console.

The trailers for Dawnguard and Hearthfire both outright stated that it was exclusive, and even went so far as to include the Xbox logo wipe thing.

The trailer for Dragonborn has nothing of the sort, and no (legitimate) information I can find else where says it is intended to be a exclusive.

You can take what hasn't been said as evidence to facts.