Can this System in the future be the end of HF Communication across the Atlantic Ocean??
I doubt it. This system allows the controllers to track the aircraft, not talk or CPDLC to them at the moment - there is no two-way communication via the tracking satellites. Even CPDLC has it's failures occasionally and they have to revert to HF which is why the aircraft using CPDLC still have to carry out a handover procedure when crossing the control boundaries and carry out a Selcal check.
So I hope I can receive with my own Equipment ADS-B signals via satellite from the North Atlantic Region in the future!
I doubt that the satellite will be re-broadcasting the ADS-B signals on an aircraft band frequency - more likely to be up in the GHz bands and with antennas pointing at the ground station. With 66 satellites around the world and 22 and maybe more over the horizon at any one time, how are they sorting out which satellite got the signal and reported the data 'back to base'. A satellite can't send it's own interrogation signal and have every aircraft in it's view respond. I've dumped all my ADSB/TCAS books but isn't the maximum range that generates a response about 75nm?