Will we eventually see the Big Six in the US?

As the Big 3 continue to lose market share (short-term reversals due to incentives notwithstanding) and the next three largest automakers (Toyota, Nissan, and Honda) make further inroads, it's looking as if the US may be migrating towards the European market structure. There, seven manufacturers each hold roughly the same share of the marketplace, which is a significantly different structure than what we've witnessed here in the US since the industry was born. This would mean less of a gap between the largest and smallest of the major manufacturers, along with increased diversity in the marketplace. We could expect fewer big "knockout" hits and possibly an increased number of niche vehicles, especially those that crossover traditional market segments (and we're not just talking about minivans that want to be regarded as SUVs). External factors could change the timing of this and in extreme cases, even the final outcome. Consider, for example, a dramatic change in energy prices, a breakthrough in material technology, or even a wholesale change in vehicle architecture (think "skateboard" for a moment). Until that happens, though, the competitive advantages that each company enjoys continue to shrink, and that'll mean thin margins, more frequent model refreshes, non-traditional marketing efforts, and a continued focus on quality.