JavaScript lets you listen for multi touch events just fine with touch starts, ends, and moves, and lets you keep track of each finger separately. What gestures would it not be possible to implement with that?
The browser has a bunch of behaviors that get in the way. The Ionic team could speak better to what is preventing them from implementing these gestures, or you could browse their issues to get an idea too: https://github.com/driftyco/ionic/issues?utf8=%E2%9C%93&q=ge...
10 open, 40 closed issues related to gestures in v2. It has not yet reached release stage, but already good enough to start the development of the new apps.
Do they have a ViewPager? A DrawerLayout? Swipable rows in lists (eg: to delete an item)?
Also v2 is not the best thing to point to because it's very new and I don't think many people are using it compared with v1. And closed issues don't necessarily mean fixed, eg: https://github.com/driftyco/ionic/issues/9052 -- I believe all WebView based apps suffer from the problem described in this issue.