That's definitely NOT visible from todays announcements. The App Store for Mac is an extremely good idea, but it's entirely optional. There'll still be a lot of software distributed through "classic" channels, as the App Store will of course be closely guarded and most probably won't allow porn, pirate tools or anything else Apple deems unsuitable. Aside from those issues, a lot of companies will want to offer more licensing options than are possible through the App Store. However, it will be a great place for individuals to get their consumer-level apps from and it will take a lot of burden away from people who have to support them.
Conclusion: It's optional, not a lockdown for Mac OS.