@ darre(20x n)
Avast! has a long history of offering free products, such as the free version of avast! antivirus, which I have been using for over seven and a half years and it existed before that.
Now that could obviously change (no one is going to give a forever guarantee), but the current policy is that there will be a free version. So I rather doubt there will be no free version of avast mobile security, but there could be a different feature set in the free mobile security product and 'if' there were a premium product.
If you don't like that idea I guess you could keep using Threat Aware until your license expires.