I also heard that you can get coins immediately from gyms, but I don't think that's true. To this point, the longest I've held a gym is about 18 hours, but I've never gotten anything but EXP.
You have to manually pick them up. Go into the shop and click on the button on the top-right. I've put my pokes in gyms all of twice since finding this out and it's worked immediately both times.
Considering just how many more Pokemon there are to add? Yes. Sue me, I'm an optimist.
Like, you would need to buy a ridiculous number of expansions or make room.