You never know what Hobie is going to do until it "hits the street". When the Adventure first came out, it was sure a pleasant surprise to me. Likewise with the Revolution and Island. They're always improving their products though, so you just never know.
The Adventure is already pretty fast. Basic dimensions, hull shape and to a lesser extent, weight can make a difference, but I wouldn't think that alone would be enough to spur the expense of an adding an additional boat. There is certain to be a point of diminishing returns.
Like you, I prefer to go fast. As I recall, you have a Tandem. It's a very nice boat (we also have one), but when it comes to speed there's no question the Adventure will blow the socks off either of the tandems. Additionally, there are some "tweaks", modifications and accessories that will further improve the performance of the Adventure (and others). Then again (as you know), your own conditioning level has a rather significant effect on speed and range!
Looking back 10 years, Mirage Hobies are lightyears ahead of the first "Classic"; there's every reason to think in another 10 years they will have a bunch of even better boats. Until then, I'm thoroughly enjoying what they have today and will eagerly consider the next slicker and faster boat when I see it!
Sorry I don't have a better answer -- maybe someone else does.