I find myself in the very same situation.
I too use a 7D and currently my longest lens is also the 70-200 f4 IS.
I have been waiting for what seems like ages for a new 100-400. Everytime I thik it's around the corner, Canon just manages to announce something else that is close but not quite the same (70-300L, 200-400).
However I am in no hurry and am still waiting for all the pieces to unfold. I am also considering the 300 f2.8 II or the 200-400, but I'll wait and see what else might come up next year.
In retrospect I now think I should have gotten the 70-200 f2.8 II instead of the f4 version. Not only for the larger aperture advantage but also for the ability to use the 1.4x and 2x teleconverter more eficiently especially at 400mm.
I have to disagree with neuro. I don't think the 70-300L qualifies as a replacement for the 100-400.
The main reason most people buy the 100-400 is precisely to be able to get to 400mm ! The strenght of this lens is the long range.
It's a lens that is even more useful on a FF, that doesn't benefit from the 1.6 crop factor. So the 70-300 would never be enough to replace it.
Besides if Canon can have three different 70-300 lenses (EF - L - DO) and four 70-200 lenses why couldn't they replace a very old 100-400, particularly since it's the only one available with that important focal leght ?
The recently revealed patent for a new design (100-400 f4-5.6) and the frequent rumors of several versions of this new lens being tested gives me some hope that sooner, rather than later, we'll be seeing it announced.
Regarding your situation, I also share the opinion that if you really NEED it, you should get it. You can always sell or trade it for the new model without loosing too much money.
However if you, like I, can aford to wait a little longer, maybe next year could bring some surprises as well as some confirmations (like the price of the 200-400), and we'll be in a better position to make a decision.