As much as I'd like to see proper tileset support (and better sprite/animation tools) and real-time multiplayer, I think now is the time in Construct's lifecycle for it to become a little more refined. We have a lot of features to play with now - so many more than when I bought the software not even six months ago. The growth has been phenomenal and some of the features have been substantial additions. But many of these features have come at such a pace that they're still not properly documented or covered by tutorials. I guess that will come with time, so long as we're all given a chance to let the new features soak in.
My thinking is that, for the next few months, Scirra should focus on tightening up the current offerings, and I think a debugger would be an excellent place to start. After that, I love the "modularity" idea to help those developers with large projects.
After that, some attention to the IDE would be great. A better way to organise multiple event sheets and layouts would make me a very happy man, and collaboration tools would go a long way to place C2 on the map.
I'd also really like to see some progress made in the exporting side of things. It feels too messy right now - too confusing to new users with, frankly, too many options. We need a single, all-encompassing, mobile exporter that will unify development and reduce new user confusion. Then that exporter needs to be tweaked, refined and documented thoroughly. Node-webkit also needs some attention - its own object to be specific; using browser actions for what is considered to be a desktop application is counter-intuitive.
Good luck guys; it's great to see that community feedback continues to be one of the driving forces at Scirra.