I know what you mean. I'm sure someone will be along any minute to either tell you skinnies will never die or to lecture you for taking notice of trends, but if you're thinking of investing significant money, it makes sense to think about longevity.
I'd say the difficulty with a big purchase right now is that the current situation, where you can find pretty much any jeans shape on the high street, is very unusual. I'm going from memory (which is getting less reliable) but normally when a trend changes, one style gets a stranglehold pretty quickly, whereas this has been going on for a few years now.
I think it's great that we've got all this choice, but because it's (possibly?) unprecedented, I'm wary of predictions. The only thing I think we can say with reasonable confidence is that the direction is away from skinnies, which got so extreme there was nowhere left to go.
So if you wear jeans a lot, my best suggestion is to throw yourself into it. We may never have this much choice at our fingertips again so why not make the most of it, try out a couple of shapes, but maybe hold back from investing too heavily in any single style?
Sorry if that's not quite the advice you asked for! If it helps, I don't think any shape will look dated by next summer - the change is normally very slow.