Exactly my thoughts.

The blockchain we know as Steem will still continue to run, but it will have lost its exchange listings, main dapp, and therefore most of its value. We will have to start all over to get exchanges to list it again and they will do so under another name like "Steem Classic" for example.

Trying to fight our way back would involve a lot of explaining to do. There are even long-time Steem users who use Steem and Steemit interchangeably. The original chain would probably have to be renamed. It would go the way of the earlier Steem forks pretty much into obscurity. Does anyone even remember Whaleshares any longer? Golos has a whopping $0.8 million market cap.

The exchanges are key. Without being listed on major exchanges, a coin has no liquidity. No liquidity means no monetary value. Of course, the chain will survive but only as the playground of a few hard cores.

On the other hand, the user base is what Sun really wants. The question is what the current user base of Steem is really worth. 40,000 daily active users or so might be big for a blockchain supporting social DApps but it's a drop in the bucket in the larger world of social media.

I really don't know exactly what to make of this, yet.