RE:Before the end of this decade....
From my understanding a few things have to be developed and or changed. One of the big things is the aircraft itself (materials) to withstand the stress. Then there is the cost per mile/passenger/fuel. If you google it you can get a pretty good idea where things are advancing and where problems are.
My opinion I see tests and more serious talk happening once BBD, GD and Dassault get their latest projects up and running towards the end of the current decade. Unfortunately I think the other two have ahead start just because the are already in the defence and jet fighter business. But who knows BBD can always pull a rabit out of their hat. It would be great if they would be able to build one secretively and surprise the world.