Figured I would start a thread about the new RPi5 before we get a lot of questions. I did just pre-order a board, active cooler, and 27W power supply from Sparkfun.
From reading about the hardware and Jeff Geerling's video about it, I don't think there will be any issues running OMV 6.x on it as long as they release a new Debian 11-base image.
The realtime clock will be nice. USB performance should be faster since there are separate usb controllers and both USB3 ports will run at full speed at the same time. Now that it has a pcie connector, I imagine there will be some good pcie to sata hats. And I'm sure people will be excited about the power button. vcgen will be able to give us power stats. It might be time for an RPi plugin.