There's finally a date—a Mac-only (no iOS) pilot program launches May 2, and you can sign up today to be invited to the beta when it opens.
Cloud syncing will replace, not complement, the existing Wi-Fi sync. For people who still want Wi-Fi sync, they'll be re-implementing it as a local version of the same protocol used by the cloud sync service, and they're not going to commit to whether local Wi-Fi sync will be ready the same time as the cloud service.
Finally, only once they've performed "scalability testing" will Cultured Code know how much the service will cost, and therefore whether (or how much) to charge for it. I kinda hope they do charge for it, if only as a last 'fuck you' to everyone who's whined about how long the sync service has taken to build.