Blizzard hasn’t stated. So anyone offering any answers will be purely speculating.
The first indication we can expect is when Blizzard announces the details of the next Remix, probably.
Note that a lot of the collectables in Remix are simply boss drops in normal MoP (dungeon, raid, and world bosses) so available for the RNG grind. But there were some recolors and unique models that were only available in Remix, and there is no information about any future availability.