Strategy Analytics confirms that tablet shipments have stalled. Apple also saw a decrease in number of units shiped and a reduction in market share from 29% to 25% mainly due to the strength Android (70% market share).
It’s interesting that tablet shipments have peaked at approximately 50 million units per quarter. This is much less than smartphone shipments that are at around 290 million units per quarter and still increasing. While it might seem more attractive to specifically target smartphone form factors, you should also consider that smartphones are replaced more often, in extreme cases, sometimes within a year. The installed base is probably larger than quarterly shipments might suggest.