For anyone lucky enough to have an X-E2 already this will be a very important update for you to do as it adds phase-detection AF support to the existing X-Mount lenses.
The update also adds Lens Modulation Optimisation support which aims to give the very best quality images possible for each lens.
As far as I am aware (and Fuji don’t mention anything) the firmware update doesn’t make any difference with any camera other than the X-E2, but it’s always worth updating the firmware as often small bugs are fixed that aren’t mentioned, as well as it being good practice to keep things up-t0-date.
Head over to the Fujifilm website to download the firmware here
Updating is simple. Download the firmware and copy the file to an SD card, put the card in the camera and then press and hold the DISP button as you turn the camera on. Press OK, choose Lens and follow the instructions. You can download the firmware for all your lenses and copy all the files to a single SD card and the camera will install the correct firmware for the right lens saving you a lot of time and messing about.