If you develop a second sugarbush that has good slope but no power you would have to buy a gas powered vacuum. It's not difficult to do, but it is expensive and requires some maintenance, fuel, oil changes, ideally under a roof... Also you will need a releaser that has its own cleaning, maintenance...
Or you could run 3/16 and get approximately the same yield with way less capital investment/ overall headache.
I don't think anyone is saying 5/16 is on its way out. In some places it works really well. It's just we have other options that may be just as good in certain situations.
30 x 8 Leader
Home made AOF / AUF
Hood / pre heater
Indiana LR gas powered vac
750 taps @ 25"