, a staff member at Unity, has indicated the following on the Unity Forums - see http://forum.unity3d.com/threads/5-4-beta-and-oculus-1-3-ovrplugin.394524/
5.4 betas work with 1.3.0, you will have to extract the plugin dlls to a slightly different path, ex: C:\Program Files\Unity 5.4.0b11\Editor\Data\VR\Unity\Win64 for the 64-bit windows OVRPlugin.dll. We will begin shipping the newer plugin in a future beta.
Oculus has not done as much testing on 5.4 beta builds so they are hesitant to recommend them for shipping products. But please do test them, they are fully compatible.
I have tried this with 5.4.0b11 and the OVRPlugin for Unity 5 V1.3.0 and this appears to works fine with Oculus Home and my DK2. Of course this is a beta version so not suitable for published products yet. But this may be useful for others using Unity 5.4 beta in their Oculus VR developments.
Also, could Oculus take a look at their web page at https://developer.oculus.com/downloads/game-engines/1.3.0/OVRPlugin_for_Unity_5/
as that indicates the plug in is only for 5.3.4p1, whereas Unity is now at 5.3.4p2. So should that read "5.3.4p1 and later