As excellent as it was, I'm not saying that SpringOne/2GX has replaced JavaOne.
The week before SpringOne/2GX, I took two of my sons to the StrangeLoop conference in St. Louis. This conference covered several important areas of software development. There was good coverage of Java and alternate JVM languages and frameworks, along with a bunch of other languages and technologies. It wasn't held in a big conference center or a nice hotel, but in three different buildings, each with a unique atmosphere. This “small” midwest conference featured industry luminaries that you might have expected to see only in the Moscone Center. To see them on the stage of a St. Louis night club was something else!
Just this afternoon, after opening registration less than 4 days ago, the CodeMash conference in Sandusky, OH, sold out. This conference, like StrangeLoop, covers a broad range of technologies. Though there is a bit more .NET than I would like to see, :-) it is another excellent event, bringing speakers from across the country and attendees from across the globe.
I could go on. There is the Silicon Valley Code Camp, the Houston TechFest, and so many more. But you get the picture.
For several years now, JavaOne has been turning into more of a vehicle for pushing a certain technology (coughJavaFXcough). The attendance has been gradually dropping. As developers stopped going to JavaOne, they began to find other events to meet the need that JavaOne was not filling. Or they started their own.
The Oracle acquisition and the subsequent decision to make JavaOne an afterthought to Oracle's annual event didn't help, but JavaOne was already on its way out. It was destroyed the way so many companies are: by pushing what it wanted its customers to have rather than providing what its customers wanted.
So I can't point to a single conference that will be the new JavaOne (although Über Conf comes close). But I can look out at all the technical gatherings happening around the world—Devoxx, JAOO, the JAX events, the GR8 events, and so many more. And then I can look closer to home and see all the “small” conferences that are providing big benefits to attendees and speakers, and I can say it without a doubt. JavaOne has been replaced.