That will depend mainly on the replacement board and if 8 allows the change without the need to...? do it all over again which usually is what many would want to avoid.
When the new supply for the present 2010 build cooked a brand new board after the clean 7 install back then I swapped the first mb with the exact same make and model and Win 7 didn't require reactivation. I haven't had that situation since I still only have the 8 RP presently seen on a VM to say if you could do the same with the new version.
A different model board even by the same company will however force the need for a fresh install of 8. The chipset and other things could be enough of a difference including the drivers
where a fresh install would be advised. Any other make and model would automatically require a clean 8 to start off all over again.
The main reason you might run into a problem even with the exact same would be from an updated hardware profiling seen in 8. You may want to back everything up just in case you have to go that route ahead of time.