For me the "pure" all-flash array is just not sustainable and I think the industry needs to get away from the thinking that there is something "magical" about an AFA - that is just marketing.
At the end of the day it is just hardware and software - I see no reason why a company who focuses on a small number of storage platforms cannot overtime optimise their platforms to work optimally with flash and HDDs - that way we avoid silos.
The problem for the vendors that have "pure" AFAs, that have no support for HDDs, is that they have no motivation to optimise their hybrid arrays as their strategy is all about claiming that a "pure" AFA is in some way special.
The traditional hybrid arrays will continue to get further optimised for flash over the next few years and we will reach a point whereby products like Violin, Pure, XtremIO, etc. will just not make sense.
I would just love for a "pure" AFA vendor to explain what their product does that a hybrid array like 3PAR, VNX and FAS cannot do (either now or overtime) - certainly we all agree there is a whole bunch of things a hybrid array can do that an AFA can not.
Will it be quicker for an AFA to have all the features of a established hybrid platform or the other way around?
Based on the current trajectory I would say the established hybrid platforms will catch up with the AFAs first and I do not think that will be far way.
Just my view of course and I might be proved completely wrong - only time will tell.
I wrote a detailed blog on this subject over at http://blog.snsltd.co.uk/does-the-all-flash-array-really-make-sense/ recently.