"Hey guess what? Tomorrow you guys will finally get to see the
#Halo4 stuff I've been working on at 343! I'm anxious, hope you like it."
So, this could also mean that we won't just see some sort of in-game reveal like Reach. I'm guessing we will see something multiplayer related because he is the level designer, and he did say:
"Tomorrow you guys will finally get to see the Halo 4 stuff I've been working on.."
Well, I can't wait ;)
See you tomorrow!