[Geisty]

There is a bug when you add someone to your party and you are sitting in the Adventure Menu that causes a new menu placeholder called "Arena Mode".
It also reveals the purple tickets to be called "Invitations",

Also, currently, if you position your cursor correctly, I can see the titles of yet to be released missions.

The first Wardog Fury placeholder is "Short Fused"
The second WF mission is called "No Reservations"
The second Council Apocalypse mission is labeled "Cyborg Station".

I dunno if the devs care about this stuff being revealed but, hey, there it is. Interesting.

[Drimakus]

Wow, nice catch! And yeah, lucky-lucky you, seems like I don't see any of these..

[Geisty]

Yeah my friend caught it when I invited him to an Xbox live party last night, And that's really weird. The Arena placeholder disappears really fast but the titles should still be there. You have to maneuver the cursor almost like you're trying to target something behind it.

But the Arena Mode leaves a lot to speculation. As do these invitations.

[SygBoss]

I assumed the tickets would just be for inviting friends to missions they haven't bought yet, since the icons only appear when you're in a party.

[Geisty]

That makes the most sense to me. Tbh, I was hoping the purple tickets would be used for something interesting.