Certainly a worry, but it looks like high quality CPR (strength, frequency of compressions) was performed almost as soon as Hamlin needed it, with restoration of pulse relatively quickly.
It's all rare, but one encouraging comparison would be Fabrice Muamba. He had CPR performed for 78 minutes when he collapsed and 15 shocks from an AED. He of course retired, but the 10 year anniversary came up and he gave an interview last year where he seemed normal.
At this point I'm a little worried he has ARDS given they flipped him prone. I've since heard some facilities are more liberal with the usage of intermittent prone positioning as prophylaxis.