I like trains and commuting by train too. I can't stand traffic either.
But cars remain awesomely effective, because they can go from point to point, and they're so competitive that trains are only really competitive if:
* you're going to be traveling for very long distances (but not long enough for airports to be faster), or
* traffic is going to be utterly miserable, or
* the train is RIGHT THERE and very convenient
or, ideally, some combination of the three. (Driving to the commuter rail and having your office be Right There is an acceptable incarnation of point three).
Notice where trains are most effective: the northeast corridor (really dense population, traffic problems, city centers with workplaces served by train/metro), big cities on the west coast (e.g. SF, Seattle).
There are significant diseconomies involved in making a big dense city. "A future without cars" looks like some of those cities and those city's problems - in particular, really expensive housing, especially if you want to raise a family and have multiple bedrooms (or, God forbid, a yard). Remember that median household income in the US is only $44k. If you're reading Hacker News I'll guesstimate you're probably making double that, maybe triple.
Anyway. Gas prices and the relative prices of train commuting/car commuting/real estate may change the dynamic of transportation in the future, but I don't think the densification that it entails is an unabashed good for the common man or that my preference for trains is a substitute for comprehensive realistic transportation policies. And if we must go down that road (so to speak) we're going to need to do a better job of making effective, useful, cost-efficient transportation projects than we have over the past few years.