Since you're going to do a major fix in a few years and since it sounds like you're doing the work yourself, you can get by with minimal effort (I believe.)
First, you didn't say if you know if your floor is uneven because of the sub-flooring or because of the top-layer / finished flooring or because of the joist / support system (under the sub-flooring.) With that, I have no direct answer for you BUT you could rip everything up, shore up (sister) the joists (if they're the problem), and just install a 3/4" plywood sub-flooring. You can install padding and carpeting on top of that and be done with it, essentially, forever. If you think you'll need to temporarily 'remove' any of the sections of sub-flooring later on, just screw those pieces down. Be sure your horizontal seams don't line up w/each other. And be sure to lay your sheets PERPENDICULAR to the joists. Use a chalk line to 'mark' your sub-floor as to where the center of the joist lies under the sheets. If you feel there's a moisture, use EXTERIOR grade plywood.
If the unevenness is DEFINITELY due to the 'waves' in the finished layer of flooring, simply remove it and install padding and carpeting on top of the sub-floor (assuming you don't find problems under the finished flooring, after which you'll end up doing what I mentioned just above.)
Unless I've misunderstood your situation and question(s), that's that. My best to ya and hope this helps.