The released was obviously expected and we discussed how to best transition to a new version as effectively as possible and it was brought up in IRC and I'd mentioned the transition on the forums here before, as well as it being constantly in the RC list.
http://df.magmawiki.com/index.php/Dwarf_Fortress_Wiki_talk:VersionsObviously everyone here thinks that the way it was done wasn't the best, but I urge you to read some of the opinions that were presented before the upgrade that people went forward with to try to make the transition effective.
I'm not going to go out and explain the rationale for how the wiki was planned to be prepared for the new version (the above link should do that), but in all the time when it was discussed I wish as many people cared as apparently do in this thread.
Basically the way it's being done is to ensure that DF2010:Subject articles contain ONLY up to date info, and 40d: contain ONLY 40d info (and 23a contain only that).
But I'll address the OPs points:
1) It's all still there, and the parts that are exactly the same as DF2010 will be available in the DF2010 when it's confirmed (and a lot isn't the same).
2)And all the information still exists for 40d, not just in history but in actual articles. Though it might be a couple clicks more difficult to reach.
3)EXACTLY. That's why it is how it is. All the information is STILL There, and STILL labeled as 40d only, or DF2010 only.
4)I'd calmly ask you to ask questions
before you start insulting people who want nothing more then to make something useful for you. You'll note I'm not calling you an idiot/moron even though you apparently couldn't find information even with a very obvious search button.