I am hoping like hell this ends up being the case. Give me power, a place to put my own stuff and some details on the CAN bus and leave me to it.
I do not want to pay a premium for your slow, locked down, buggy / seldom-updated touch screen.
A lot of Bluetooth speakers today can fill a car with a sound wall better rear speakers used to. Apple says you just need two of their Bluetooth speakers to fill a room in a house with great stereo and reasonably good surround sound. The square footage of a car is generally smaller than the supported room size.
edit to add: if Slate is successful, I wouldn't be surprised if a decently sized ecosystem pops up around easily installed custom sound systems and the tablets (possibly with headphone jacks!) to control them.
No, because they knew what they were getting into when they bought this truck. And I'm sure there will be a dozen DIY ways to add a more traditional sound system.