It’s always tempting to wait, but the Twitch is really an excellent controller, so I doubt you’d struggle too much to sell it on. I suspect a LOT of people with other controllers are waiting for the Twitch 2 as well, so they can snaffle up an original Twitch as a secondary portable controller…
I’d buy the Twitch now, and if in 9 months a second revision comes out, sell it on and upgrade. Plus, you’ll have spent those months mastering it, improving your skills and having a massive amount of fun. Oh, and you’ll get Serato DJ with the Twitch for no extra cost – who knows whether the Twitch 2 would come with the full version, or just the Intro version instead… hard to predict…
In summary, if you think you’ll like the Twitch, I’m almost certain you will love it. And actually, even if you’re not that into it in theory, once you’ve had a go most people love it anyway.
I know I love mine 🙂