I don't quite get what the problem is: you are safe to assume that your new garage door opener will come with a new remote (actually two as is customary these days). I honestly don't think you can reprogram the old remote to work with newer openers because almost all (perhaps just all?) new garage door openers use rolling code signal scrambling technology and if the old remote can't generate rolling code, nothing you can do about it - it requires a specialized microchip.
Usually people are concerned with using <strong>newer remotes</strong> with <strong>older openers</strong>, not the other way around simply because it's easier to lose a remote than to install a new garage door opener. I have to say this is the first request of its kind, so I have to ask if I understood your question right: you want to install a new garage door opener but save an old remote and use it on the new opener? Â