It seems kind of sad. I'm sure Ruger put a lot of time, money and effort into those rifles. I suppose there was no way a few years ago that they could have predicted what would happen in the AR market.
Back when dealers could charge $1,200 for a plain jane Colt 6920 and sell every one of them before they even got put on the display rack, it probably was a lot easier to sell a piston Ruger for a few hundred more. Ruger also put expensive features on the SR-556 that folks no longer want to pay for. Expensive metal sights, proprietary handguards, etc.
I wonder, though, if they would put their piston system in an AR-556, and sell it for around $700, if people would buy it?