No change. Just because your radio is "software defined," doesn't change physics and signal processing math. There are 'best' ways to use a given piece of spectrum, and while a SDR can make your hardware more flexible, it can't change that the most efficient way to use spectrum is usually to have a dense set of subcarriers modulating amplitude and phase. By avoiding a strict multiple-access protocol on a band, everything just gets worse; probabilistic back off is inefficient vs hard-scheduling. Every wireless system I've worked on (satellite radio, WiFi, LTE) has been very spectrum constrained, so I dont really believe in this future where spectrum is cheap.