Wrong 
Clsssic WoW requires a base sub and a lot of people play that as well, probably more so than retail once TBC comes out and I promise you that there’s no amount of cash shop in TBC classic that will have that effect you’re seeing in retail.
I think their sub numbers will only continue to grow and stay steady and while the cash shop does help, you’ve yet to provide any proof that it’s become their most profitable model even over classic wow/tbc subs.