as long as they dont change the steinberg “grace period” policy you will get the latest cubase version license when activating. but make sure you buy a new license that has never been activated.
also if you are planning for few years maybe you better wait for cubase sale from steinberg,(unless you got a really good deal with 3r party retailer) i think they usually have one per year,40 % off usually. now they have discount on upgrades from lower cubase versions. they have also the competitive crossgrade price option if u got other DAW license(see a list on cubase sell page)