I think it's highly unlikely you'll see CarPlay or Android Auto in a Tesla. Now that Tesla has a data plan that will soon be in place, having them add these features means time/money spent that would only serve to reduce a revenue stream. It's in Tesla's best financial interests for you to use the music streaming and GPS navigation they provide and not your own.
The big question should really be: How long is Tesla's contract with Slacker? Once that ends, hopefully Tesla will switch to Spotify for US users. A few years ago Tesla even floated the idea around of creating their own in-house music streaming service. Hopefully they decide not to go that route!
So for now, US owners need to either get used to Slacker or live with streaming from the phone via Bluetooth. At least you still get skip, play/pause and song info via the screen. So unless you like to move between playlists frequently, you still can do the most common controls via the wheel and not have to touch/look at the phone.