One of the first X-series cameras that Fujifilm released was the X-E1 (nicknamed Sexy One) in 2012. It was just the second interchangeable-lens camera to feature an X-Trans sensor. And it was a big hit (stores couldn't keep it in stock), at least for a moment. People loved the design and retro rangefinder aesthetics. It was plagued with programming issues that quickly gave it a bad rap. Fuji later resolved these problems with firmware updates, improving the camera to what it was intended to be.
In 2013 the X-E1 was replaced by the nearly identical X-E2. It featured the updated X-Trans II sensor, and had a few other small improvements, but was essentially the same exact camera as the previous model (without any of the issues that gave the other camera a bad name). It didn't fly off the shelves at the same pace that the X-E1 did when it was first released, but was overall a good selling product.
The X-E2 was replaced by the X-E2s in 2016. The "s" added to the end of the name most certainly stood for "same" because the differences between the two models are very tiny and insignificant. This camera didn't sell particularly well, partially because it wasn't really any different than the original X-E camera from 2012 and partially because the much-anticipated X-Trans III sensor would come out just a few months later.
It was rumored that Fujifilm had intended to discontinue the X-E line. There were some credible sources that said Fuji had no plans for an X-E3. But then customers took to the web and made their voices heard. There were a lot of people asking Fuji for an X-E3 with the new X-Trans III sensor. And Fujifilm listened.
The current rumor floating around is that the X-E3 will be released this fall, just in time for Christmas shopping. Not many details have been revealed, except that it will be slightly smaller (yea!) than the previous three X-E models. And it will, in fact, have an X-Trans III sensor.
I'm excited for this because I would like to give the new X-Trans sensor a try. My X-E1 is five-years-old (although I've only owned it for about nine months), and so it might be getting close to time to relegate it to "backup camera" duties. I love the design of the X-E1, so I want to stay within the X-E line. In other words, the only camera that I'd want to replace my X-E1 with is the X-E3.
And by replace, I mean that I would keep the X-E1 but just wouldn't use it as my primary camera anymore. I can envision pairing a vintage lens with it and keeping it in that configuration. It's a good camera that creates good images, so I don't think it will sit on a shelf collecting dust. At the same time it has more than a few clicks on the shutter and it won't last forever, and if there is something that's the same except a little better, that would be the ideal successor.