User blog comment:Kogath/Monster Hunter XX Discussion/@comment-20314792-20170204130747/@comment-27120688-20170204180946

There definitely will be. A third trailer is expected soon. My guess is that trailer shows off the new Hunter Arts on some previously unknown returning monsters. Probably get another deviant showcase there (2 or 3 more), and perhaps a peak at G rank. Famitsu will likely do 1 or 2 more issues after Feb 22nd (which is there next issue on MHXX).

You can also expect ~10 or so hidden monsters within the game when it releases. That in itself takes time for people to discover everything.

If it were my guess, expect AT LEAST Gravios and Monoblos in the game, especially since Basarios and Diablos are both in, usually they all come in pairs (save for MH3G w/ Diablos). Another monster like Lao that invades fortress is being hinted at, so likely Shen Gaoren. The first trailer teased G. Thunderbugs, so probably Yama Tsukami. Lore wise, Lao Shan Lung is running from Fatalis, which is why it mostly ignores you, so maybe that hints at the Fatty Trio coming back. Molten Tigrex and Lucent Narga are probably going to be end game rare's in this one, along with the end game variants from 4G (Raging Brachy, Chaotic Gore Magala, Rusted Kushala, etc.).

My guess is that these would all probably never be mentioned until people play the game though. If they were to show off monsters in another trailer, I feel like Nerscylla, Gigginox, Qurupeco, Gobul (re-worked), and Lunastra are the biggest choices, since they all bring something unique while not serving as end game monster material.