I am reading how Nimble (now HPE) starts its public block storage cloud. Nimble  (also NetApp , etc) places storage servers in Equinix’s data center, colocating with AWS/Azure. In such way, Cloud instances can use storage directly from Nimble and bypass EBS.
Since Nimble just a sub $1B company (before acquisition), such initiative may not be prohibitive. But it does give storage vendors an entry into Cloud.
What is missing in this picture?
I/O to EBS goes to (host) storage network while accessing Nimble or NetApp is most likely through VM network. In a not untypical setup, storage access through VM network will hit speed bumps.