Technically if you obscure the fact that previous
contributions were
made under version 1.1, then you are saying that you don't consider
any to be available under 1.1.
IANAL, but that sounds like complete nonsense to me.
Wikipedia doesn't have the right to
change the "or later" clause to suit its purposes really. It is
accepting contributions under a perceived contract and it should put
them out under the same. If any user could reinterpret contracts like
that than a future version may be produced which may not suit an
author who wanted to stay with version 1.1 or 1.2 and it is not up to
wikipedia to say they can't, or imply they can't.
When you post something to Wikipedia you are trusting that the FSF
won't release a new version that you find unacceptable - if you don't
trust FSF not to do that, don't post on Wikipedia. (As I understand
it, "or later" clauses aren't legally valid in all jurisdictions, so
you may have a point depending on exactly where the people involved
are.) Wikipedia can impose whatever restrictions it likes on posting
content to it (give or take a few exceptions, possibly) and you always
have the right not to post to Wikipedia.
On the other hand, there is the possibility that
wikipedia could say
they are offering all content under a single specific license, and not
"version or later", and they would seem to be fine. It is only the
bumping out of old versions that worries me as the author could still
legitimately download a copy of the information under version 1.1 if
it was derived from before the license bump. It is actually pretty
simple to figure out, a simple check to see whether the contribution
was made before wikipedia changed to 1.2 should be sufficient.
Wikipedia is using the content under version 1.2, you are releasing it
under version 1.2 or later. Another user can use it under 1.1 if it
was released under 1.1, just as they can use it under CC-by-SA if it
was released under CC-by-SA - that has nothing to do with Wikipedia.
Remember, you aren't releasing the content to Wikipedia, you are
releasing it under a free license and Wikipedia is then using it under
that license.
The text at the bottom of the page with a reference
to another page
which adds conditions is still quite unclear to me. If the following
were at the bottom of each page it would eliminate the necessity to go
to another page to discover that the license linked on the page
contains an optional restriction which wikipedia uses.
"All text is available under the terms of the GNU Free Documentation
License version 1.1 or later with no invariant sections."
It's already there. As I've said before - follow the footnote. (That's
the * at the end of the statement - click it and it will take you
further down the **same page** where the details are.)