Scott, chances are it wont be unlimited, but virtually unlimited, as in, very high allowances compared to now. Even the current Ultra plan with 50/50GB satisfies most customers on Gen4.
As for changing out the Gen4 equipment, that shouldn't be happening because I want to say the Jupiter 2 and Jupiter 1 satellites will use the same radio and modem. Though it's highly possible Hughes will have an entirely different modem/radio for Jupiter2.
If you are on the edge of the current Jupiter footprint, those are the only areas where you will be installing both Jupiter1 and Jupiter2 equipment, as Jupiter2 most likely will only be used for the Central portions of the states where Jupiter1 can't reach. If you are close to the east coast you will only ever deal with Jupiter1 unless Jupiter2 manages to somehow cover the entire USA it self.
Nancy: Another result of the 50G at night is to influence large data transfers to the less used times of day, eliminating their potential impact on the day-time users. Just another variable in the complex management of satellite Internet.