Until they actually succeed at putting a cork in it the upper bound of the damage can't be determined- like I said, this party's just gettin' started (and unlike Ixtoc-I it's in-our-face, there's no avoiding it, or the longer term effects.)
But even if they plugged it today (and I sure hope they do, but I'm not holding my breath), it'll still be the largest single-event environmental disaster in US history. I'm glad not to be dependent upon Louisiana fisheries for a living.
But whether the F150 remains the commuter-car of choice in 5 years depends more on Chinese energy policy than the costs of environmental damage mitigation in the Gulf of Mexico. China is currently burning ~1/3 as much oil as the US, but is on track to be using 2/3-3/4 as much by 2020, exceeding US consumption by ~2025. There aren't enough drilling rigs in the world to keep pace with the increase in Asian appetite- US efficiency will be enforced by the market: People driving mopeds & mini-cars short-haul in India & China are willing and better-able to pay a much steeper price per gallon than a 100mile/day suburban commuter in an F150.