The seed server I'm running probably can't handle all of them doing bootstrapping at the same time, but once they're bootstrapped and have their own lookup tables stored locally, theoretically it should scale much better than a traditional centralized app since individual messages and status updates won't need to be coordinated through any single server.

Of course, the Telehash version I'm using is very old and unsupported, so there's no guarantee that its integrated DHT can handle any significant scale.