I'm not with Laminar Research, just a fellow simmer in the UK.
If I understand you correctly, your intention is to purchase a valid copy of XP11 from LR directly, either the digital download or a DVD set and initially run it on Linux based PC. Then, maybe next year, after you have purchased another new Windows based PC, you then what to run your purchased copy of XP11 on that instead?
The short answer is yes, if previous posts on this subject from LR themselves are anything to go by!
When you initially purchase a digital download version of XP11, you will receive a Product Key by email. If you purchase a DVD set, then this will also ship with a Product Key, but this is hidden and embedded in Disc No1 and not viewable by the purchaser/user!
For the former option, your PC will always need an internet connection, both for the download/installation and also to run XP11, as LR will periodically check for a valid licence.
For the latter option, whichever PC you use, you will always need a DVD ROM drive, as Disc No 1 always has to be available to XP11, for licence activation purposes.
Anyway, getting to your point, when you get around to purchasing a new Windows based PC, all you need to do is download XP11 again onto this machine, and use your existing Product Key to activate it. If you have the DVD set, then re-install XP11 onto the new Windows PC, making sure that Disc No 1 is in the DVD ROM tray at all times, post re-install.
During the time you are running XP11 on the Linux based PC, I would suggest that you don't purchase any third party addons, just in case there is a conflict whilst transferring over to Windows.
This is my understanding and I hope it provides the clarification you need.