Someone posted this guy on Reddit and ZakPak even talked about it on YouTube.
Quote from reddit: In one of the hologram mirrors in the LM3 E3 booth, an orange ghost with weird, alien looking antennas on its mouth-torso was seen by the public but never in any gameplay demos or the Treehouse Live footage. Its antennas do move around a bit on their own, so perhaps they use them to attack Luigi by grabbing and thrusting him into their torso, which appears to have a separate mouth. It also has baby hands (this is the 5th regular ghost type seen now, the other 4 being the Basic Blues with a gold Speedy Spirit variant, the Thwomp-looking Slammers that charge at you, a skinny yellow/gold ghost that behaves similar to Hiders and the purple ghosts that sneak up on Luigi and presumably grab him, a mixture of Grabbing Ghosts and Sneakers)

I don't know why Nintendo hasn't talked about him yet. Maybe he could be a ghost shown later in the game?

I think that the blue (antennas) are actually the tongue (like Zakpak thinks) and maybe it wraps around Luigi to grab him or slaps Luigi with them. I think Luigi would have to grab the tongue to slam it (and now that I think about that, that might be the way you defeat boos? I'm not sure though.)

[There should be a GIF or video here. Update the app now to see it.]

It reminds me of the original Gold Ghosts in Luigi's Mansion too