It is not required to install all successive versions. Depending on the leap, sometimes ESRI recommends an intermediate version, but I'm going from 11.1 to 11.5 when it's released and I'm not worried at all.
Like Zach said, it *probably* should be fine. I would do it. We are on 11.3 and will be going right to 11.5. Coming from any of the 11.X versions wouldn't scare me except maybe 11.0 but even that would probably be ok.
When Esri releases 11.5, Esri will provide all the versions you will be able to upgrade from in their documentation. For 11.4, you can upgrade directly from 10.8.x or higher. So for 11.5, I would definitely expect a direct upgrade from 11.2 will be possible and supported.