I HAD to swap out a motherboard literally 2 days after doing that free upgrade to Win 10, and the new motherboard was from a completely different manufacturer.
 
I was prepared for a complete reload of the computer, but just decided to see what happened booting up with the new motherboard.
 
AMAZINGLY, Win 10 detected the swap, and did some internal adjusting of whatever it felt it needed to, and then proceeded to boot up just FINE.
 
I did have to go back in to re-authorize a few applications, but other than that, it worked like a champ.
 
That this worked for me is indeed because Microsoft finally abstracted the hardware layer with Windows 10 - and I was quite impressed with the results.  
 
WAHOO!
 
Bob Bone

abacab
I have not tried this yet, but have heard reports that Windows 10 has a newer method of abstracting hardware, where the motherboard and chipset changes are taken in stride now.  Where in past versions,  it used to take a sysprep or a repair install to get the OS working on the new hardware, it should no longer be necessary.
 

Swapping the motherboard may... or may not trigger the need to re-authorize Windows 10.
I've experience both...  
Worst case scenario, you'll have to give MS a call... and with a short explanation, they'll get the copy of Win10 authorized.

Jim Roseberry

abacab
I have not tried this yet, but have heard reports that Windows 10 has a newer method of abstracting hardware, where the motherboard and chipset changes are taken in stride now.  Where in past versions,  it used to take a sysprep or a repair install to get the OS working on the new hardware, it should no longer be necessary.
 

Swapping the motherboard may... or may not trigger the need to re-authorize Windows 10.
I've experience both...  
Worst case scenario, you'll have to give MS a call... and with a short explanation, they'll get the copy of Win10 authorized.

I don't mind a phone call
 
Clean installing Windows due to a hardware upgrade ... ugh!!!
 
I have heard that signing into your Microsoft account and linking your Windows 10 digital license entitlement to your account may speed up the re-authorization process.