Despite Microsoft's ultimatum to Yahoo running out, there is no official next move yet from Redmond. The WSJ has published reports now that cite sources close to the matter that Microsoft leans towards hostile takeover of Yahoo at this point.

An announcement could come today from Microsoft regarding a hostile takeover.

Additionally the WSJ reports that Yahoo is set to announce to run Google search ads within a week to counter a hostile takeover by Microsoft. As reported Yahoo already tested Google ads.
The advertising deal with Google would be implemented in a sort of bidding system. Yahoo users would see an ad from Yahoo, Google or others depending on which one pays the most. Such a system would avoid apparently scrutiny by regulators.
More details on the WSJ.