Does Sencha support JAWS?
Ext JS has ARIA support and we are testing Ext JS against JAWS 16 http://www.freedomscientific.com/JAWSHQ/JAWSHeadquarters01 as well as older versions.
Each Ext release 4.2+ adds additional Aria tags to our generated markup (that these readers evaluate). Ext 5 adds more tags, (and the new Ext JS 6 framework, were our developers are working on, will even contain more ARIA tags).
Go ahead and download the Ext JS trial version, so you can try it for yourself.
Let me know if there is anything I can help you with!