Virtually, yes. Almost all modern routers support uPnP to an extent. Most routers won't support the newer versions of uPnP, but those are drafts anyway and don't need to be worried about.
I know that current Comcast, TWC, and Verizon FiOS routers support uPnP, and almost all modern third-party routers also support it. If someone doesn't have uPnP support, they should just learn to port forward on their ancient router or install DD-WRT.
The point here is to attempt to simplify the set up of a private home-hosted server. If the user's router is ancient or misconfigured, then they have to go in and do it manually.
Offering QoS support as well with simple language like "Optimize my connection for server speed" or "Optimize my connection for general traffic" could also be good, but is a side thing.