Hmm, I'm curious about this too. I don't see why not, since I've used programs that were designed for older versions of Windows before. Don't plan on upgrading just yet anyway, but... it's good to know for future ref.
There was a PSA on Tumblr about SAI not working in Win10, but apparently it wasn't true and the original post was deleted. I haven't upgraded to 10 myself yet since I was out most of the day, but the program should work if you run it as admin or in compatibility mode.