Tablets have hit an impasse. A few years after the iPad made the device common, the market has mostly split in two: There's the high-end "2-in-1s" like the Surface Pro, and the low-end slates like the Amazon Fire. With many people still happy with the tablets they bought earlier in the decade, the middle ground has shrunk.
This chart from Statista demonstrates this. Citing data from IDC, it notes how worldwide tablet shipments have steadily declined on a quarter-by-quarter basis since Q4 2014. Last quarter, for instance, they hit 38.7 million - a year-over-year drop of about 12%, and the lowest total since Q3 2012.
Now, just because shipments have declined doesn't mean there's no business in tablets whatsoever. Apple, for one, saw better-than-expected revenue from iPads last quarter, in large part due to its iPad Pro selling at a higher cost. Still, unless something unexpected happens, there isn't much reason to think a new wave of tablet sales is on the horizon. Statista