One of the big design conceits of Theros block was the division between hero, god, and monster mechanics. However, that didn't mean that each set would use the same keywords to represent the central players in the Theros story. For Born of the Gods, the big monster keyword - monstrosity/monstrous - was replaced with the slightly similar tribute. Since tribute is an opponent's-choice mechanic, and thus feels somewhat like a drawback, many people were dissatisfied with it compared to monstrosity.
When cervantes3 asked Mark Rosewater on his Tumblr blog, "I really liked monstrous. Does it have some more design space to it, or has it run its course?" Mark replied:
There is more design space left. I strongly doubt we’ve seen the last of monstrous.
The kind of delayed-kicker effect of monstrosity that represents the creature "hulking out" is a pretty universally applicable flavor trope. It can be equally well applied to Innistrad-style scary-story monsters like Werewolves and Vampires, or to a completely different setting like one with magically-irradiated futuristic Mutants.
In other words, monstrosity isn't necessarily likely to return in Journey into Nyx, but our best chance to see it soon might be the second Innistrad block that's almost sure to happen given the popularity of the first.