Yeah, this is a good question, maybe we'll not get a definite answer now(,because the plans can be uncertain), but let's try:
Will all pets be made heroic? If no(or uncertain), is it known what number(which) of pets will be made heroic? Original? More? If yes, how many(or which)?
And will there be other-unique heroic pets?
Would be good to know (if the plans are more or less certain ofc), for some vague planning, although we don't know the exact stats.