I've never played a Metal Gear Solid game in my life, but apparently people are excited about it crossing over into MHP3. If you remember, a couple of months ago the new Metal Gear Solid game announced there would be missions involving Tigrex and Rathalos.
This time round, MHP3 will feature an exclusive armour that ensures you look like Snake (Male) or The Boss (Female). Felynes will also have access to a different armour and the ability to hide under a box. Apparently there will also be MGS sound effects.
Also in that link, you'll notice that in the 3rd picture down the Hunter and Felynes are standing in a sort-of brown area with a map icon that immediately made me think of an arena. Interestingly, it looks different to the MH3 Arena... Of course, it might not actually be an Arena, and it's in a strange position relative to the basecamp... I don't know.