Whether there'll be an appeal or not we don't know yet. McLaren have confirmed they have submitted notice to appeal, but currently there are no grounds on which they can appeal as far as I'm aware.
That said, that steward apparently did say that they
could have given a 10 grid penalty at the next race (would have been even more dodgy, given that it was this race the offence took place in, and Hamilton finished). How, I've no idea, as it's clearly written in the rules that it's a drive through or 25 second penalty.
Kimi's argument you naturally have to question. Though it would make little difference to him personally, just that of his team, he would say that, wouldn't he? It is the same argument that Trulli put forward though, and the one I've been repeating since before the penalty was even handed out.
Hamilton's defence of the move is rather weak in my opinion.
"After allowing Kimi to completely re-pass, I crossed from the left side of the track to the right side of the track, passing behind Kimi in the process. I then attacked Kimi on the inside of the first corner, and successfully out-braked him."
Clearly from the moment he came back onto the track he was working out how he could best gain from the situation.
If the penalty
is for cutting the chicane and the initial advantage gained, it sets a worrying precedent for the future, where a driver can attempt to navigate a corner, perhaps with the minimum of effort then rejoin and launch an immediate attack. British media, Hamilton fanboys and some others are saying that F1 is a farce because of this penalty. For me, the bigger farce would be if you can launch such an overtaking move by simply cutting a corner.
If you
can get around the corner, you should do. The general consensus is that Hamilton could have got around the corner, though perhaps with some risk to both cars. Even had he decided he could not, had he just ran off the circuit on the exit of the right-hander, then rejoined when Kimi's car was clear, he'd have had a minimum of an 6 point lead (assuming he won and Kimi still retired), possibly even a 10 point lead (had Kimi not retired and finished where he was).