Having ridden BoltBus (similar to Mega but they allow bikes and they don't use double deckers), the product is appealing to the sort of folks who travel with iPads and iPhones, not low income folks. (Power at every seat and free wifi!) The bus lines have, I think, mostly pulled people from the trains (ie: Amtrak regional service) in the Northeast, whereas the Acela is what competes with the air shuttles.

Outside of the northeast (and presumably a handful of other potential markets)? I suspect the impact will be negligible. You're not going to take the bus to ATL to connect to the west coast.