SatelliteGal,
To answer your specific question, yes the Superdish will need only 3 cables (one for each satellite location, 119, 110, and 105).
So for now, you could run four RG62 cables from your Dish500 to a switch 64 inside your house and then feed the outputs to four receivers.
When you upgrade to Superdish, they would replace the dish and swap out the SW64 for a DP34 using only three of the four cables from the dish. Then, if any of your receivers are 4 digit model numbers, you need a Dishpro legacy adapter ($70) located within 10 feet of each receiver. If the receiver is a 3 digit model (i.e. 301, 5xx, 721, etc.) the legacy adapter is not required.
It remains to be seen if they will actually charge for the legacy adapters.