Large FC deployments will take a long time to move away from, for those already using iSCSI/NFS/SMB it's a bit easier of play. The replication scenario actually can benefit from some of the HCI gear....where you can set prioritization on VM-level replication and vm-level deduplication could prove very powerful in the right scenarios.
At least from the VMUG's I've been at this has been hard pill to swallow for some orgs. Budgeting wise some places plan on alternating SAN, compute, and network over a multi-year rotation. Bringing in a solution slowly is fine but on the backend also marrying the org to a single vendor solution is a tough pill for some to swallow. Not saying it shouldn't be done but sometimes the easy button doesn't always makes sense *coughs SQL Server installs*.
I'd also add that not only do compute, SAN, and network have their own life cycles due to changes in technology, usable part duration, and increasing maintenance costs, but the shared storage business is beginning to move away from the "pay a maintenance premium as years go by or replace your entire array" business model.
SSDs, when properly cared for, can last over a decade and some AFA manufacturers warranty the drives for 7+ years or even a lifetime warranty. If you're no longer stuck repurchasing your storage every ~5 years then HCI makes even less sense since you'll not only be paying higher maintenance costs on the entire stack as years go by, but your only recourse is to replace all of your compute and storage simultaneously to move onto new nodes. Ripping and replacing a 5 year old HCI infrastructure might be administratively easy, but extremely costly.
Also, HCI doesn't solve the issue of storage complexity that really started the HCI movement. When I first heard about HCI I was managing a VMware datacenter with HP EVA storage arrays and it was maddening. HCI seemed like a great alternative to complex storage platforms, however, HCI still makes you decide on redundancy factors, replication factors, turning dedupe on/off, compression on/off, encryption on/off, Erasure Coding on/off, CVM CPU and RAM, etc. Storage shouldn't be hard, it should just work.
Nutanix has a great software platform and software suite around private and public cloud management, consumption, and monitoring but HCI as an infrastructure doesn't really make anyone's life easier.