After the 3.0 is out everything will work better.
I am almost positive apple and probably google, will not create an app for instant messaging, mainly because there are so many other universal clients.
You could buy anything from Beejive IM for $15, to Nimbuzz which is free. Most of these applications even support VoIP. If you want a good idea search for "IM client" or "google talk" in the App store.
Personally, I am waiting for the 3.0 to become public before spending money on any IM clients. Just to be sure I get one with push notifications.