I'm surprised Nike never marketed replica shoes back in 1989 when the movie first came out. Sure, it wouldn't have the power laces (likely never will), but still, it would have been cool. So now they should do that either next year for
BTT2's 20th anniversary(!!) or in seven years in 2015.
Mattel should do the same for a Hoverboard replica. Even if it's just a standard skateboard, recreate the design. I'd just remove the wheels and stand up in my room as a prop, since I've yet to get ahold of one of the replicas I see floating around online.
EDIT: On a related note, Nike's website lets you customize your own shoes. In 2006 I spent $100 to get a customized pair of Bruins that look very close to Marty's 1985 Nikes for my McFly costume.