I think federation has largely moved to the device. I do most of my messaging on my phone, where which app I'm using isn't invisible, but it's also not really a hassle to switch (mostly it involves dragging down my notification shade and tapping on the message I received). Not perfect, but also not really requiring the cognitive overhead that switching between desktop clients seemed to have. My phone federates my contacts, email, calendars, etc without much input from me and I believe chat will go that direction as well.