I think you're right about MS and I think maybe Sony were pondering a secure system themselves as I expect they were under a lot of pressure from Western (?) games publishers to put something in place. Or their share holders? I dunno but whatever the details it does indeed look like Sony have scored a huge coup for now.
Will MS review their overly restrictive 2ndhand game policy? Yeah. At some stage for sure but I bet they'll just run with it to see what happens first. Big Corps always like to suck it and see first and the only way they'll change is through sales so it's over to the customers and their buying power. Message is simple - as you say - Sony all the way!
Or a PC of course!