We're seeing usage of Construct 3 growing 30% YoY according to all our stats. Perhaps it could be optimised better, but it's a rate we're happy with.
Looking at stats from Construct 2, we decided to reduce the free edition limits on events when moving to Construct 3 because we observed a large population of users who didn't convert to paid users indefinitely - the free edition met their needs whether this was just for fun or in a different environment such as education.
FWIW the total # games submitted in GGJ we don't consider a pretty reliable metric, Construct submitted games have been pretty static (like other engines for the most part) and it in no way seems to correlate with growth or other successes we're seeing in other aspects of the business.