SO Mighty No.9 just got a publisher to make their games have a physical retail release and since it was a Kickstarter game as Project Ukulele, I think we can have an idea how they managed this. They seem to publishing with Publisher Deep Silver, currently for Xbox One, PlayStation®4, Wii UTM, PC, Linux and Mac.
Their Kickstarter has a Q/A section regarding this topic on: http://www.mightyno9.com/en/faq6
I've pasted the entire thing in this spoiler:
Maybe Playtonic can check this Publisher out since they seem to be able to publish in several platforms and of course they are helping an indie developer have Physical Retail Releases. What do you guys think!?