With EMC now being owned by Dell, Dell having nothing useful in their old portfolio, and HP having only performance to brag about I wouldn't be surprised to see NetApp climb in market share over the coming years just because they have such mature software surrounding the storage. There really are unique things they can do that the other vendors can't, like Shift, or the strong integrated backup suite. I didn't mention IBM because people don't tend to buy IBM storage because of choice, there's usually some other driver. Now that flash has pretty much levelled the performance playing field software is the only differentiator and from what I can see none of the other vendors have really pushed into that area the way NetApp has. Sure, they tick the boxes, but I've never seen the software in use while NetApp customers tend to use the full stack.
That said, cloud is going to trounce the lot of them shortly, even with the NetApp cloud integrated features I don't think they'll get very far when workloads become native to public cloud so if they can even keep revenue flat I'll be amazed.