It still have a possibility, but saying 90% of altcoins will fail is not a good prediction.
what makes him said that ? if this prediction not based on some fact, it is only speculations.
Well if you want facts, here are some you might find interesting:
(at the time of writing)
1) There are 1,545 coins/tokens listed on coinmarketcap.com
2) The cryptocurrency market cap is currently at $489,379,690,258
3) The top 100 coins/tokens alone (6.47%) account for $469,263,573,711 (95.8%) of the total cryptocurrency market cap
I know this doesn't mean that the bottom 93.53% are failing, but it's no secret that they're far behind. A large majority of them could fail and no one would notice. His prediction may be overly harsh, but I'd say it's not too unlikely.