That's the wrong question. W3C itself is relatively tiny, and has fairly ordinary (albeit well tuned) software/server infrastructure. Reproducing the legal framework would be more of a pain, but even that could probably be done. But W3C is mostly its member companies, and the're not switching, since the majority of them, including all browsers, were in favor of this. So if all existing specifications continue to reside on W3C's web site, and all new specifications continue to be produced (by member companies) in the same place, there's not meaningful forking possible.
If members are disgruntled, you can fork. That's happened before when there was disagreement about what to do with HTML, and it led to the creation of the WHATWG.
By and large, members this time are supportive. Not all, mind you, but all the large players.
The only party with the capability of "forking" Internet standards as we know them is Google. Because as the majority share of web browser traffic an extremely dominant percentage of web server traffic, Google can define the Internet as it wishes, and everyone else has to follow along or fall behind. This is the same with EME. Standards organizations stay relevant by accepting what Google gives them, they would simply be left behind if they didn't.
(For those who don't know, Widevine, the DRM scheme that is currently best known as compatible with EME, and which taints my Firefox browser so I can watch movies, is owned by Google.) http://www.widevine.com
(Sidebar to the sidebar: Widevine has the least Googley website you've ever seen. Stock photos of a physical padlock, HTML code entirely based on table tags for layout. It's so strange.)
I doubt it. Specifically, I doubt they will, or even want to. That's not really what they do, they are mostly advocates.
As advocates,I'm sad to see them do this. I will still donate to them, but it's unfortunate to see them quit. This means they will no longer have a seat at the table for future discussions.
They still do enough good to be worth donating to, but this was not a very good choice on their part.
If members are disgruntled, you can fork. That's happened before when there was disagreement about what to do with HTML, and it led to the creation of the WHATWG.
By and large, members this time are supportive. Not all, mind you, but all the large players.