You could conceivably start your project now and finish with no problem. But in my opinion the chances of everything going right are going to be pretty slim.
Not only might there be problems with compatibility (the most recent physics update broke all previous physics games), but there will most likely be problems with obsolescence.
That is to say, you could be coding things one way for a few versions, then all of a sudden a whole bunch of buggy code that you just hacked together to make things work right can be done with a couple proper new features.
And yes, you could dig into the code and rework everything to conform to the new, proper way, but it would be a major hassle. Especially if the bulk of your game engine is built around an obsolete hack-job. I know this from experience.
My advice is this: Construct is in beta. It's not finished. Don't expect to make a finished project with it right now, you'll just give yourself a headache. Instead, learn everything you possibly can about it and simply plan you game. Tinker with Construct and find out how it works. Report bugs and make feature requests.
In the mean-time, complete everything else that you can for your game. Graphics, sounds, music, whatever. Get that ready to go. Then when Construct gets to 1.0 (or at least closer than it is now) you'll be able to assemble all the pieces of your game relatively quickly.