As market competition for space access heats up, there is a renewed interest in air-breathing technology. At the same time, remarkable launch cost reductions in more conventional boosters are imminent due to the efforts of SpaceX and other firms.
It is beneficial to everyone to explore alternate technological paths, since no one can predict which paths will pan out and produce an economical and reliable vehicle. Most or all of the concepts currently under consideration use winged vehicles to avoid vertical takeoffs and to reduce the required engine size for takeoff. Work on more advanced concepts is also underway.
Currently, two countries, Japan and India, are in the planning stage while the British company Reaction Engines will soon begin a major test of critical engine components of its Skylon vehicle concept.
For more information see NSS Board Member John Strickland’s article in The Space Review: Current strategies towards air-breathing space launch vehicles.
I don’t know if I’d say winged vehicles are all that dominant. Of the vehicle families under test, SpaceX, Armadillo, Masten, OSC, Blue Origin are all VT; SpaceX Dragon will eventually be VL; I do not believe OSC will be a lander (and perhaps unmanned) but the other families are al VL as well.
TSC/Scaled Composites SS2, Lynx and Sierra Nevada are winged; Reaction Engines is winged but still unflown and not manned even when it does.
The future of Earth to Orbit operations will be a mix for now; time and the market will be the final harsh arbiters of which one is economically best.
Oh, and not to forget Boeing CST-100 and Atlas V…