Only one Nexus device in history had a microSD slot, do you know which one it is?
That's right, out of all these devices, only the Nexus One — the very first Nexus device — had the option to expand upon the 512MB that came on board with it. That was all kinds of important, since the card could fetch you up to 32GB on top of that claustrophobic half gig. By the time the Samsung Galaxy Nexus was released (8 months down the line), internal storage had gotten cheaper, so we had 32GB available from the get-go. In short, it's been over 5 years since we last saw Google agree to a microSD card.
It's entirely possible that, should it ever come down to Google making the choice, microSD card will become extinct. And it's not just the maker of Android that sees the benefits of ditching the slot — as mentioned, manufacturers do usually bear the brunt of any related complications, not to mention that there's quite some money to be made in selling phones with larger capacity storage. Combined with the ever more ubiquitous cloud, that's enough incentive for handset makers to drop them. Whether we like it, or not.