Removing the cap would be a boon for employers but would seriously undermine wages for software devs here, I imagine.
India and China each graduate many times more software engineers each year than does the US. Many, perhaps even most, would love to work and stay in the US.
With a massive influx of engineers in a short span of time, I can't see how wages would remain where they are now in areas like NYC and SF. This is probably exactly what the Facebooks et al want, I guess.