The following schema sum up HTML5 activities functional architecture.
Because it will force independence from Gtk/Python, HTML5 activities is a first step toward Sugar on Android.
The very first Web Activity is Wikipedia. Wikipedia is a Python activity embedding a WebView to display HTML Wikipedia pages. Searching and browsing is available from a standard Python toolbar. Clicking on a toolbar button change the current HTML viewed page or launch an history command (previous/next). To communicate from HTML to Python, Wikipedia embed an HTTP Server. When a hyperlink is clicked in the HTML page it call the HTTP server then run Python code.
HTML5 activities has been choose  as a feature for Sugar 0.100. HTML5 activities will be build on WebKit2 but if time permits we will implement compatibility with previous releases running WebKit1. HTML5 activities is accepted a project for Summer of Code/2013.
Some interesting discussion around this subject in the community:
- Sugar Web Architecture 
- Sugar Web UI 
- Localization 
- Renaming HTML --> Web 
- Running HTML5 activity on other platforms 
- How to deploy framework in the activity 
- Datastore API 
- Unit Testing 
- Webkit1/Webkit2 compatibility 
See TODO list of the project on .