I also have heard nothing, but like Hunter said you have a few options:
1. Move to google admob mediation. It is quite simple to import from adwhirl and the code changes are minor. Though unlike what Hunter said, this is a new team that did not build adwhirl, but they have supported it the last few years.
2. MoPub, not much info though many have used them. With MoPub Online, you can serve up to 10MM impressions monthly before you need to sign a contract or pay a fee. We offer MoPub Premier for customers who want to exceed this number or sign a separate agreement with us. We do not charge a percentage of revenue; we charge on a flat CPM basis. From their FAQ (
http://www.mopub.com/resources/faq/).
3. Mobfox has something
7. You can set up adwhirl on amazon yourself and pay for it
I am sure there are more, just google for them. Of the ones above, I can tell you my opinion of those that I have some knowledge on. Google mediation is a solid choice for most people, easy import options from adwhirl, google backed servers and support. The bad with admob mediation is that it's closed source so if you want to modify something you have an issue here. Note, that all are closed, except if you set up your own version of adwhirl. I looked into Smaato and Nexage a few years ago, both are solid options, though things may have changed. I opted for my own version of adwhirl as it gives me more control that I need and want. If you have lower traffic though, you could technically fall into a free tier on AWS at Amazon, but you still have to put in some effort to set it up.
Good Luck and we can only hope Google extends the deadline a bit so more of us can get our smaller/older apps updated.