They probably wasn't planning there Skyrim game when they told us about them, it was lore found in in-game books which they thought would make it iinteresting for players to spend time doing things other than hacking away at bad guys. Then got to Skyrim and saw the difficulties related to putting them in the game and decided to focus on improving other mechanics which is where other developers may of done things differently and left there core gameplay and other features rather thin because there were working on too much. I can see why people may of been dissaponted in not having them and perhaps Bethesda Development team were dissapointed they didnt get time to get them in the game properly, but by the look of the gamjam stuff we might still get them at some point.
And not to cause a disagreement on future games thats a long way off, quite a bit of that may of changed, they are now under the control of the Aldmeri Dominion who seem quite keen on Opression so if government and religion didn't change in Elsweyr it would be breaking other lore.
See, I don't buy that?
1) How is it hard to implement the Volkihar. Tunnelers of New Vegas burst from the ground, Spriggans IN SKYRIM come out of "the walls" (trees to be more specific). There's no reason Volkihar can't use these scripts.
2) A certain faction in Skyrim are werewolves. Instead of werewolves? Make them werebears. PROBLEM SOLVED. Yes it'd be nice to have both, but if there's truly time restraints, I think werebears, according to established lore, imply the werebears take precendence over werewolves. And hell, what are werebears? A re-skin of werewolves. That's literally all they are. Not that hard to implement....
3) You can watch the "Making of Skyrim" video on Youtube and they specifically state they chose Skyrim "because it had the most established lore." Then they proceeded to rip it apart.

Sort of off-topic, but if we went to Elsweyr in TES VI and the Aldmeri Dominion governed them? I would actually be ok with this. Why? Because Skyrim provides reason to believe such an occurance is plausible.
Smooth, natural transition. That's what this change in the Volkihar lacks. One moment they're popping out of lakes, the next moment they're pimpin' it up in castles and watching Underworld movies all day.
Skyrim is 200 years after the last canon lore for most of the issues in question
Which is a cheap excuse and a poor writing technique. If you're just gonna say "THE NEXT ELDER SCROLLS WILL TAKE PLACE 8923895928357 YEARS IN THE FUTURE" to alleviate yourself of any responsibility to your own lore? Then don't bother with lore. Either commit or don't commit, but don't half-ass it.