Not in the current package format. It's been discussed before and some of the issues raised included:

• Impolite or improper to put someone else's package in your own package (though this can happen with permission, such as my XSLTsearch in Warren's excellent CWS package)
• Difficult or impossible to handle new versions of dependent packages (should the new one be used, what if it breaks something you depend on, did the url change, is the old one still available at all, etc.)
  
  
• Difficult to validate the dependencies in any useful way that would work with all packages

The result was that this might be worth doing in the future but for now, simply note in your package that it depends on another package that should be installed first. That way the end user has full knowledge and control and each package is as clean and focused as possible.

cheers,
doug.