That stymieing might take one of several forms: A developer of an app you love might release a brand new version with a brand new price tag, since theres no option to offer upgrade pricing. An app you love may be forced to strip out features you depend upon to comply with Apples rules. Or developers behind an app you love may find that they simply cant keep the app in the Mac App Store anymore, and pull it (see Postbox, Alfred, TextExpander, and Moom, each of which has been forced to move out of the App Store and return to a direct sales only model). Whether youll be able to cross-grade from your Mac App Store version of that app to a standalone, external version will be at the whim (and maybe even technical expertise) of the developer in question.
While the Mac App Store remains a fine place to buy certain software titles today, the issues are real, and Apple thus far has displayed its characteristic determination to stick to its current plan. If youre concerned, you have two tools you can use: The first is to stop shopping at the Mac App Store when possible, and buy apps direct from developers instead. And the second is to share your feedback with Apple directly.
Its definitely too soon to panic about the future of the Mac App Store and OS X. But its not too soon to be concerned.
[Lex Friedman is a Macworld staff writer.]