Turns out we done all know it
"As we all know they are largely fading away mostly not refreshed the second time."
(Disclosure NetApp employee, opinions are my own etc etc)
Sorry wrong on both counts .. from where I sit, flexpod sales to new accounts are looking really healthy, and they don't use a rip and replace upgrade strategy in any case, so theres a lot of evolutionary growth throughout the stack over time in the existing customers. Thats one of the advantages of independent scale at each layer in the stack, as compute network and storage don't always need to be refreshed simultaneously (usually they don't, network tends to stick around the longest and compute cycles through the fastest)
I think vBlock used to be rip and replace at the end of their maintenance period, but they were built to be a large scaling unit, good in their own way, but the last time I looked they seemed to have moved towards a more flexpod like way of doing their life cycles. In any case DMC seems to be more focussed on VXsomething so maybe the vBlocks are fading at the hands of the incongruity of Dell selling Cisco servers.