They could have yes. But then again, we don't know where the profits from these two companies were going towards when they were paid to the treasury. If it was something critical or highly controversial that was being funded with the profits, where ending funding by stopping the NWS would have been highly unpopular, the stuff could take some time to sort out to not have a big effect, idk.
Otherwise, they could be waiting for the Senior preferred restrictions to expire in 2018. Maybe they don't want to give away any impression where congress may try and interfere with the shares.
The timing of ending the subsidies for Obamacare seems interesting though. Why did they end it now when they could have done the same months ago? Upcoming court decision? Settlement? Documents? I don't know but the timing of it is interesting.
Also, even the media outlets which are anti GSEs are admitting that they're generating profits and are profitable companies so I don't think it's a question of if they'll stay or go anymore. I think the narrative has changed from wind down to keeping them.