ipadaThis year is expected to be another incredible growth year for tablet sales, but research firm International Data Corporation (IDC) has issued a word of caution for the coming years.

About 221.3 million tablets are expected to ship around the world by the end of the year, according to IDC. The company revised that forecast down about 3 percent from its previous estimate of 227.4 million. Yet, those sales still represent a more than 50 percent increase from last year.

IDC reported that a combination of factors from market saturation worries in the United States to larger smartphones cannibalizing tablets in other regions will slow growth to about 22 percent in 2014 and the single digits by 2017 when around 400 million units are expected to ship.

Android’s market share will have grown to 59 percent by 2017 while iOS will have fallen to 31 percent, IDC forecasts. Windows will make up about 10 percent and other operating systems around half a percent. A little bit more on that point from this handy IDC chart shared below:

OS IDC Tablet Data