You can definitely wait and install/activate your purchase at a later date. Some say they will wait for the next version of CB to be released so that they will receive that version during the “Grace period”.
As far as a warranty on software goes. I attached a link to the official terms and conditions. But, as far as I can tell, the Steinberg Shop which is run by “asknet” would probably work with you. BTW… it is doubtful that Cubase will not work on your Win 10 computer. So I would not worry about that.
https://shop.steinberg.net/c/shop?ml=EN&page=policy.terms
Regards 