If you have not used the free version, try that first.
Otherwise construct is a great purchase. I would imagine anything you learn with construct 2 should apply to 3.
Also, this is a stable and feature filled engine. Even if 3 came out tomorrow, construct 2 would probably be at an advantage/offer more than 3 would for some time.
In game development you need something stable and reliable. Waiting for a brand new engine is not the best idea typically.
Construct 2 also has many plugins, something that a new engine will need time to implement.
TLDR: Construct 2 is still a good purchase.