Hypothetical and unlikely? You're talking about legislation that is supported (if not written by) groups that don't exactly have a sparkling track record of being reasonable and not abusing any bit of power that they're given or feel that they're entitled to. Take the Universal/Megaupload fiasco for example.
The Wikipedians are taking action so that "unlikely" isn't even a possibility.
And while Wikipedia may be a central resource, it's not the only or primary source of information (see all the citations). At most it'll be an inconvenience but one that will prove a point.
http://en.wikipedia.org/wiki/False_dilemma (link may be broken due to political protest)
The only people currently taking Wikipedia offline are Wikipedians themselves. Anything else is hypothetical and unlikely.