The biggest thing is getting away from capacity-based pricing issues.
Once you get beyond that, any other concern is about the support that you get from the vendor. Does the architecture lock you into a particular size or can you scale and grow effectively? Is there an internal limitation that might not work for you? In other words, where is your bottleneck at? You need to ask how you'll get beyond it. Do you need to buy another box and manage them separately, or can you aggregate management across them?
Those are really the issues to look at. Basically, you're going to scale, you're going to grow over time. How do you grow becomes the next big thing to deal with.
San Jose Sharks opt for all-flash storage array
When should you think about purchasing an all-flash storage array?
How do you know if a hybrid or all-flash array is right for you?