Right now a lot of Nexus 9K’s are sold by Cisco. Customers are using the NX-OS mode first and then they want to upgrade in the future.
But there is a catch !
A Nexus 9K which is a spine, like the 9336PQ, can only run in ACI mode and NOT in NX-OS mode.
Every N9K NX-OS switch are leaf and when converting the network to ACI, you will have to add SPINE switches.
When you have a 9508 chassis in NX-OS mode, then the blades CAN’t be spines in the future ! You will have to buy spine blades when converting to ACI.
This is something a lot of customers think it’s possible, but it’s not.