Board Thread:General Discussion/@comment-74.129.82.112-20130314230013/@comment-5227390-20130315034954

I don't think it means Oblivion is in-accessible... just that a direct doorway linking the two to remain open to afford an invasion is no longer possible.

I don't know of anything in-game to support my claim, just seems to make logical sense to me, since others as well as the player since then have obviously frequented various planes of Oblivion with or without Daedric influence to get them there.