WHBM
I think that we should also consider incentive in this equation. Currently there is no real incentive to overcome the shortcomings of WIGE machines. If for some reason conventional aviation becomes impossible, then it may be that mankind will take another look at WIGE, hovercraft, hydrofoils, etc. Look at the electric car. The basic technology has been around as long as the automobile, but it is only in the last few years, with rising oil prices and the knowledge that the oil will run out one day, that research and development have taken place in a major way. Perhaps the real importance of these technologies is that they are there should we need them.