Who cares whether it's version 7 or version 4.2? They're just numbers, at the end of the day. Doesn't make any difference to the product you're using.
The real issue is that where Chrome updates completely silently and seamlessly, Firefox bugs you with notifications and installers every time there's an update. Mozilla needs to sort out a similar system if they want to update every six weeks.
It's fairly obvious that they don't know how to compete with Chrome, though. I still use Firefox because it's so extensible. But 90% of users don't care about add-ons beyond Facebook Photo Zoom or possibly Adblock, and they're all running straight to Google.