According to Nokia, MS plans to continue Asha. But the belief is that in the future, every phone will be a smart phone.
In order to get those Asha users to choose WP in the future, Microsoft plans to bring versions of Skydrive, XBOX and Office to Asha. That's pretty awesome for a phone that's considered a "feature phone."
Of course the versions of Skydrive, XBOX, and Office will probably be pretty bare bones and simple. But it's still pretty cool.
So not only is Asha going to still be supported; but MS is going to give Asha users some awesome apps.