Or you could use STUN and just send packets to a peer. Or use v6. Or anything from RFC6544. The reason UPnP is popular is so many home router people implemented it. If you have a real router, you have more options. As I pointed out, I have a real router and talk to people who have real routers that support things other than a 2008 version of UPnP.
Which is to say, you do not REQUIRE UPnP for webRTC. But yes, if you have a crap router given to you by your ISP (looking at you, SBC and Comcast) then UPnP may be your best bet. My point is you don't NEED UPnP if you have a real router.
I should be saying... thx for bringing me up to speed on this. UPnP is obviously not something I spend a lot of time on.