I don't see ever needing to go past 6 tuners so SWM should work. All would be Genie type.
Make sure that you don't confuse the terms "receiver" and "tuner" with one another. A receiver is a set top box. Each receiver can have multiple tuners (the number of programs that can be viewed or recorded at at time is how many tuners a receiver has).
A Genie is 1 receiver, but it has 5 tuners in it (which is why it can record up to 5 programs at a time). If DirecTV ever permits multiple Genies on an account, you would not be able to add a second Genie with a SWM dish.
To allow for more than 8 tuners in the house, you should run 4 coax lines from the dish location to the switch location. If you are positive that you will never want more than 8 tuners, then you will only need 1 coax from the dish location.