Maybe I remembered wrong but I swear when VMAX came out what 6 or 7 years ago they touted lots of controllers. And here we are 2016 and I believe they have the same number as when they started(8). Just dug up a presentation from emc from 2009 on google mentioning "hundreds of vmax engines" in "one single enterprise array".
3PAR told me at one point they can scale beyond 8 as well but the risk wasn't worth it so instead focus on making individual controllers faster (at the time it was when they first started including two 3PAR ASICs in each controller maybe 5 years ago).
EMC seems to be doing the same