Well, other than the fact that the time could be spent adding support for features that most players can use rather than wasting it catering to things a small percentage of players will ever see- or in the case of your extreme example above, that nobody can use but somebody might be able to "real soon now."
This is the same flaw as all the "OMG why not support [feature] even if you wouldn't use it yourself, add everything and let people choose" threads: Time from now to 11-11-11 is finite, the number of possible features to add isn't. "Niche" players want their multimonitor support, a few dozen people want the display on their http://www.gamesas.com/index.php?/topic/1170473-keebord-suport/ used...should Bethesda call the game "done" now and spend the rest of the development cycle in "Cater to the niche players" mode?
Except as previously stated
this does not take time. Exactly like how 3D mode does not take time. Bethesda ain't gotta do nothing.
There's nothing magical about a 4:3 or 16:9 ratio. At all. The ability to output to different shaped rectangles is just inherent in a renderer, as is different fields of view. The only thing they really need to do is design a UI that can scale well to those superwide resolutions, and that's not something that takes more time, it just has to be a consideration as you design it.
Your assumption that everything takes extra time is ridiculous, like every game engine starts out as a base and for every single little feature they have to use some of the certain amount of time they have. It's like I'm saying that the gold daggers should have little white spots, and you're telling me that's bad because they should spend the extra time on making new weapons - great, but they're making a gold dagger *anyway*, they just have to make it slightly differently.
To put it bluntly: If you don't know what you're talking about, don't talk about it. That's why I don't take part in high level rendering talk, or discussions about the realism of weaponry, because I know I haven't a clue.