What is
event.next()? Pseudo-code for what you want to do?
You can't. There's no way to delay transitions. You get notified that something is going to happen. And then it happens.
So, you can certainly do some async stuff, but... the moving finger writes, and having writ, moves on...
Only place there is an opportunity for this is at pagebeforeload, for obvious reasons. You can have your own code load page content, and resolve a deferred later after you have loaded the page. In that one case, the moving finger waits for you.
You could maybe re-write the transition hander, and monkey-patch it... I do this myself, but to simply it.
See:
github.com/watusi/jquery.mobile.simultaneous-transitions
(Only to show how you can monkey-patch the transition handler. The above I think will work in 2.x and maybe 3.x.)