This was bound to happen, as since yesterday developers have been able to update using the Beta 3 SDK and start submitting their apps for BlackBerry 10 in App World. The first ones I noticed to update are a couple of the native messaging clients, Yahoo! Messenger and Google Talk. And I'm sure Windows Live Messenger will follow soon, but haven't been prompted for an update yet.
If you don't have a BlackBerry 10 Dev Alpha device, you can still download these native messaging clients for your other device via App World.