These are two best solutions in my opinion, either go all in or all out:
SOLUTION NUMBER 1
Treat Home as R8
Give the Home album regular promo and campaign like any other regular album. Focus on the lead single, etc. In that case, I'd try to hide the fact that the album is based on a kid's movie, so it looks like the movie was made around an album (more like when they use her songs in movies nowdays) and not potray it as an album made for a movie. Basically try to make another LOUD era with extra music promo in the Home movie.
Release R9 in Spring 2016.
SOLUTION NUMBER 2
Make Home Album irrelevant
Treat the album as a non-event, maybe one performance, show up at the premiere and that's it. No music videos or any other promo campaign. Try to do it as low-key as possible, and keep reminding people that R8 (real Rihanna album) is going to be released soon. That way she can keep some of her 2.5 year hype and sales (by letting Home album flop).
Release R8 in Fall 2015.
Neither of these sound that great to me, but I don't know how better can it be. Home album ruins everything.