I watched the Enterprise Ethereum conference. They're using private chains for scalability and privacy, but hope to migrate a lot of their work to the public chain in a couple years. They think zksnarks, proof of stake, and at least the basic sharding plan will all work.

In the meantime they're being careful to stay compatible, and contributing development resources to the public project. JP Morgan is working on an open source client that bridges private chains with public.

Even using the public chain doesn't mean they're using ETH, but lots of startups on the public chain aren't using it either; nevertheless ETH seems to be maintaining its position as the dominant Ethereum currency, and it will play a unique role in proof of stake.