For someone who values empirical data, you are very quick to reject a
hypothesis using very little data. I suspect that this is because you
are predisposed towards a particular conclusion. Furthermore, that
there will be an increase in vandalism is not the only relevant
hypothesis.
We need to consider many different factors:
1) What types of vandalism are there? A simple page blanking is very
different from a subtle alteration of facts. Double edit vandalism
(two vandal edits in a row) is harder to detect than single edit
vandalism. And so forth.
2) Accordingly, what is the persistency of the vandalism on April
Fools vs. the persistency of vandalism on other days of the year?
3) How much vandalism is committed by regular users? How much by
anonymous users? What is the availability of regular users and
administrators to fix vandalism?
4) What is the situation in other projects/languages than en.wp? How
about WM wikis with small communities that aren't used to dealing with
vandalism?
5) How will the rate of vandalism this year be impacted by the
Seigenthaler incident and other media coverage about vandalism in
Wikipedia?
I also remember excellent examples were discussed last year of serious
vandalism that was particular to April Fools and that was a lot of
work to clean up after. But, unless there is a clear sign from above
that a fast and radical decision is likely given enough convincing
reasons, I am skeptical as to whether it makes sense to dig up these
threads, and to expand upon the above points. We will all find out in
3 days. You should be happy - more data for you to chew on.
Erik