Can I buy a license for RouterOS 6 level 4 and have the advantage of being able to upgrde to version 7?
Theoretically, you’d have to wait until RouterOS v6 licenses are on sale to be able tu update in the future to RouterOS v7.
In practice, you can buy a RouterOS v5 L4 license, and upgrade it to 7.x

I’ve also updated old RouterBoards that came with L4 3.X license to 5.20 without any problem
Regards
Hello,
I would like an official answer from MT on this one. I purchased a L4 licence many, many moons ago - around version 3 time - but never activated it. If I activate it on version 6 (release) will it have upgrade rights to 7? What about on 6 (release candidate) - up to 7.x too?
There is no such thing as “activating a license”. When you buy a license, you buy it for a specific SoftID.
Ok, well wrong terminology I guess. It is called a “prepaid key”. My question still stands.
I forgot this topic… but my initial question was about the x86 version.
It will be upgradable to the next version compared to the version which was on the web when you bought it. So, if you bought it when v4 was stable release, you can upgrade it to v5.xx
This is in theory. In real life, RouterOS gives you gratis upgrade to one more version (v6x)