At the heart of HyperCard is more than its object model, it's the language as well. Making Python code that kinda sorta works somewhat like maybe a litle like HyperCard seems too much of a compromise while xTalk still lives.
For Mac development SuperCard continues to live well, with support for a great many Mac OS features like scriptable drag-and-drop, AppleScript, and more, along with so many things HyperCard folks have been craving for years like multiple window styles and integrated color.
And then there's Revolution <http://www.runrev.com>, which sacrifices only a few OS-specific features to deliver something we'd never imagined before: a graceful xTalk that runs on all major platforms (Mac, Win, UNIX). Moreoever, with its group objects and lightning-fast interpreter, there's almost no need for XCMDs, as you can build just about any GUI widget you can imagine right in the product, using an extended version of the language you love, HyperTalk.