In theory, the blockchain is independent of its creator and the STEEM blockchain is hosted by independent witnesses.

So, it is possible for SteemIt Inc to fail while the blockchain continues.

Some might see this as desirable.

Of course, hosting the database and bandwidth associated with the blockchain are the primary expenses of the STEEM ecosystem; So, most scenarios that cause SteemIt Inc to fail also cause the collapse of the blockchain.

Interestingly, the failure of SteemIt Inc might actually increase the market value of STEEM as there are people who like completely independent blockchains.