Thanks for your reply!
Yeh... good question. The reason is that I have a dual boot workstation setup with Windows 10 Pro/ESXi for different purposes. And since I am not in need of any other features than ESXi 5.5 offer (and have all my VMs running) I thought I would just spare some time and keep the same hypervisor installation. At the moment, the server is running on 2xXeon E5-2670v1 CPU/LGA2011 and is therefore limited to 64G/DDR3 RAM. Reason for upgrade is to support more memory (DDR4) and Windows 10 Pro support... although the compability matrix for that as well only extend to Skylake (Xeon)... with few exceptions.
So i guess my real question is... can I find a Intel Xeon CPU that support both ESXi and Windows 10 Pro?