he isnt dead, as he falls glenn puts him infront of hit and once he gets covered in guts 'from nicholas' the zombies class him as one of own (the same thing carol done when breaking in/out of terminus) he was covered in guts so the zombies thought he was one of them. also if you watch, the intestines come out from what seems to be glenns shoulder, but it is actually nicholas's. i think that glens going to get up and hide in the bin behind him, and radio in to rick (with the walkie-talkie that was given to him) and like call for backup/help, i know for sure he's not dead TwD just wants to fuck with our minds a bit.
Another thing, every person that is eaten alive in the series, has had blood coming out of their mouth through internal bleeding etc, you can see this when michonne and the other guy are trying to get over the fence, when he falls, the zombies start biting him etc and tons of blood starts pouring out of his mouth as a result of this. This dont happen to Glenn. And also, every big character that has died in TwD so far has had such a long and big build up to their death,