But honestly though, the risk is identical to any other kernel module -- the author and future subsystem maintainer ensures it builds and works with all new and old kernels, and releases snapshots very regularly. Almost all distributions have packages for WireGuard which are automatically rebuilt with new kernel releases.
There are arguments against using it because it's still (on paper) pre-1.0 software but given it's had fairly widespread use for the past 3 years and no security nightmares it's shown to be quite a bit more secure than
[1]: https://marc.info/?l=linux-netdev&m=155323912319537&w=2 [2]: https://lwn.net/Articles/770750/