I'm currently thinking about a solution that combines a solution for desktops, tablets and mobile phones in one application. All defined stores, models, utils and most of controllers would easily work in both application frameworks.
There is already a profile system in Sencha Touch (as explained in the docs: http://docs.sencha.com/touch/2-0/#!/guide/profiles).
The general structure of the application in both frameworks is the same. The docu describes to put special views in app/view/tablet/ oder app/view/phone, same for the controllers. So why not having app/view/desktop for special views in extjs.
To decide the usage of the desktop or mobile version, I'm using the same technique as for normal webpages. So the websites decides to load ExtJS and the desktop.app.js oder Sencha Touch and the mobile.app.js.
I'm not sure, if this works and if it's the correct way to mix the application framework. Is there any sample how to correctly combine the frameworks into one project?