The software is KDE (Akonadi), Thunderbird (Lightning), and a few small utilities. It seems probable, though not guaranteed that Lightning will keep working. But I don't want to bed the farm on that, I doubt KDE will be supported, and I'd really rather just use a calendar that faithfully implements the standard instead of whitelisting the standard for certain clients.

In terms of XMPP, I checked yesterday. After updating the Android Talk app to Hangouts, all of my XMPP contacts disappeared.

In terms of email, using Google Apps on a custom domain would avoid lockin and actually not be a bad choice, at least for now. I went with Fastmail anyway, and I think it's just a better service.