The development of KDE 4 keeps going these days. One milestone achieved these days was a working telepathy plugin in kopete. Michaël Larouche showed that it can already be used for text conversation.
Sure, its just text conversation, but it shows that the basic idea is working, and that there is this kind of including possible. The next step is to put this all together with Decibel, and make it working with Voice over IP as well – and maybe also working with Video over IP.
The advantage of using Telepathy is that telepathy is supposed to be a common backend for all VoIP/IM solutions which are available on Linux. This would mean that all the effort to improve Jabber or Yahoo support would be done only once, with Telepathy. No client would have to bother with the specific protocol things, but would just access Telepathy (or, better said: the program implementing Telepathy since Telepathy is only the specifications).
And, of course, this all together is using DBus – and DBus v1.0 was just released. It also means that the new inter process communication tool for cross desktop usage on Linux has matured to a state where it is fully stable – and can be used by everyone. I’m really looking forward to possibilities arising with DBus: imaging using DBus to start a set of programs you normally use to work with in a given situation like a set of programs you use for image modification. After your worked with all of them, only one single click would be necessary to save all work in all programs and close them. Very useful, I think!