It's inevitable that Bethesda and Obsidian considered vehicles during development, but lets face it, the Gamebryo engine was pretty badly hacked together by 2008 and to this day both games suffer from more than their fair share of crashes, corrupted save files etc on console. This is conjecture, but I believe there were no vehicles in FO:NV because the console hardware of the last generation wouldn't handle that kind of thing on that engine.
Regarding "where the fuck is the new one?": Well, Obsidian developed the last Fallout game in 2010 and Bethesda followed up with Skyrim a year later, more recently Obsidian did the new South Park game... They've probably been working on other stuff along the way but outward appearances suggest they've both been preoccupied with other projects and have waited for this current generation of consoles to continue with Fallout.
I don't buy any games on release day anymore, but a new Fallout game would certainly be a "sealed copy" purchase a month or so down the road for me as opposed to a bargain bin prospect like Skyrim was (Still haven't played it yet).
