Last year, Apple began to dominate the tablet space with the iPad. In 2015, it will have a significantly smaller worldwide market share, but will still be in first place, despite mounting competition from other operating systems. Android will gain significant share, but will still be nipping at iOS' heels, and will have to settle for second place in the next four years, according to Gartner.

Where does that leave the rest of the market in 2015? Gartner believes Research In Motion's QNX, which powers the BlackBerry Playbook, will be in third. Meanwhile, webOS, which powers the HP TouchPad, will be in fourth. MeeGo will take fifth, but it will barely have any users. Gartner does not even mention Microsoft's Windows.

Last week, Gartner declared that for smartphones, Android would be first, Windows Phone be second, and iOS would be third in 2015. It appears the advisory firm is much more confident in Apple staving off competition to iOS in the tablet space than in the smartphone market.

These are predictions based on current data, but they will of course change as we learn more about the competition Apple is going to be facing. For example, Microsoft will likely push hard with Windows 8, and we already know the OS is expected to include a second, tile-based shell just for tablets.

"Seeing the response from both consumers and enterprises to the iPad, many vendors are trying to compete by first delivering on hardware and then trying to leverage the platform ecosystem," Carolina Milanesi, research vice president at Gartner, said in a statement. "Many, however, are making the same mistake that was made in the first response wave to the iPhone, as they are prioritizing hardware features over applications, services and overall user experience. Tablets will be much more dependent on the latter than smartphones have been, and the sooner vendors realize that the better chance they have to compete head-to-head with Apple."