This sort of thing has been going on for as long as I've been going to football. While I don't condone people going onto the pitch, I can understand how it happens when celebrating a goal in a moment of passion/excitement. He's not done anyone any harm. Take the passion out of football and it will be like our end at the Community Shield this year, dogshit.
People saying things like "what if he had had a knife", these type of posts are riduculous and could be applied to anything. He didn't, you have to judge people on what actually happened, not what if's.
He will probably get a ban, some of the lengths of bans for this type of thing seem excessive to me. The punishment should fit the crime IMO, and someone getting a bit excited doesn't warrant more than a 6 month ban IMO, even though he will probably end up getting longer.