Unfortunately to get into orbit at least 90% of your mass has to be fuel. That means unless there's a breakthrough we will still need multistage rockets. Skylon's a good start but still needs to carry a lot of fuel.
And even with a breakthrough that new technology may just make multi stage rockets better. Instead of SSTO spacex just get to launch more payload or fuel.
They've nominally solved airbreathing rocket engines through to the edge of the atmosphere, have you looked into the SABRE engine?
slylon could facilitate airline like service to Leo. sure it is a lot of fuel, but not stacking required and smooth runway takeoff and landings. for human transport to Leo, a skylon like ship would likely be a more familiar service, and easier logistics for fast turn arounda