Maybe release a "set two," with a very small chance of getting cubis from set one, but mostly you're gonna get new ones from it. That way it solves the problem of cubimals getting devalued as more are brought into the game!
If they release new ones they should put them in separate boxes, that way you have 1st collection 2nd collection separate without risk of devaluing *or* removing the other ones from play. =)