I do not think this has been stated publically yet, but likely closer to the final release
Until the transition is complete they will be developing both platforms, however in the long run it does not make sense to use resources to maintain two different platforms/engines
The new version is currently in bets here and will be released in early 2017
Both products will eventually use a common engine and virus database, although the programs will likely still differ in their interface and features somewhat
As you can see, they have already migrated entire avast! feature set into AVG. Only thing that really remained was Zen platform and Software Analyzer. The rest is pretty unknown. I’m sure they won’t just throw it away and it’s clearly not going to run alongside existing avast! engine allowing user to use avast! or AVG engine. The core will be just one from now one, so they’ll slowly migrate AVG features into avast! foundation they are currently using.
The reason why they will run two separate programs with separate policies is because they don’t want to alienate AVG userbase with overnight changes. They’ll bring them in gradually. Slowly boiling a frog if you will. People adapt to small changes easier than if they’d just throw avast! straight in their face and say take it or leave it. It’s perfectly understandable decision.