I kind of agree with OP. Even though Tom mentioned not considering it, I'm sure they will work out a solid plan.
Considering they moved C3 online, the last thing you want is a ton of free users using up bandwidth and data for extended periods of time. Each free user is going to be a cost for scirra as long as they can use C3 online, no matter how much they limit functionality.
If you only limit exports. A person can use C3 for years producing a bunch complete games, then just paying when they are done = Really bad business decision. Especially since they mentioned that you are able to earn money on your games even after licence expired.
If you limit events, Families, Layers and other stuff like C2, I think. it's still going to be costly in the long run as long as people access the tool online.
For me a free version should be like a tryout, get a hang of it, tinker with it, play around. If you like it... then pay for it. 30 day trial seems like a sensible option though But I'm sure they thought about it. From a purely business perspective, the last thing you want is people to abuse the Free version, and stealing bandwidth, stability, server performance, etc from paying customers, using it for months or years without paying.