Sencha Touch based apps can only work on WebKit based browsers. JQueryMobile based apps can work on all mobile web browsers.
I think you can go ahead with JQueryMobile for next 2 to 3 years. I am expecting in 2-3 years all mobile browsers will be based on WebKit engine. Once all mobile browsers start supporting WebKit, move to the Sench Touch mainly because of very good quality user interface.
