You now have one PC. And one License.
If you update your pc to a new one;
Make sure to have your registrationfile backupped.
You can use B4A on Win10 after upgrading without any problems if you do an Upgrade for your windows holding all programs.
Still it is one license and one pc.
If you then later buy a laptop you are allowed to intall b4a on it too (the second pc).
Maybe you need a new license file if b4a is counting the installs.
@Erel maybe can confirm my answer. I hope it was all ok what i wrote