Apple’s iPad may be the most successful, most popular tablet on the market, but it’s going to keep losing market share to Android as the tablet sphere opens up.

At least, that’s according to market research firm IDC, as reported in a story from PCWorld. Though Apple’s share continues to grow – hopping up to 15.4 million iPads sold in the fourth quarter of 2011 from 11.1 million in Q3 – it’s slowly losing its dominating hold over the market. Apple held 54.7 percent of the tablet market in Q4 2011. In the third quarter, its share was 61.5 percent, IDC says. By 2015, the research firm believes Android devices will overtake their iOS rivals.

It’s the low-price game that’s going to steal market share out from under the iPad, the IDC report states. Successes such as Amazon’s Kindle Fire continue to expand the market in different directions that the iPad isn’t reach. Many customers want low-priced tablets and aren’t in the market for even the cheapest of iPads. More Android devices are going to hit stores to capitalize on the lower-price niche that Amazon is currently mining, and that’s going to continue to expand the market, IDC thinks. This will continually cut into Apple’s hold on it.

Amazon’s tablet did nab a second-place finish in Q4 2012, behind only to the iPad in sales. Amazon shipped more than 4 million Kindle Fire tabs during the holiday season, not as impressive as Apple’s 15 million, but better than all the other Android tablets on the market. The Kindle Fire accounted for 16.8 percent of the global tablet market with those numbers. By contrast, Samsung accounted for 5.8 percent of the market.

It does seem as though Amazon has identified a segment of the market that it can exploit, even if it is selling its tablets at a loss. Amazon isn’t really in the business of moving a lot of tablets, it’s actually in the business of selling content. The Kindle Fire is great for doing just that. Its low price, however, basically keeps it out of contention with the iPad, and Apple CEO Tim Cook noted during Apple’s last financial report that the Kindle Fire didn’t have an effect on iPad sales, up or down, during the last quarter.

Even though the iPad continues to be a juggernaut on simple numbers, Android devices are starting to multiply. Eventually, IDC seems to believe, there will be enough of them that Apple’s share of the market will decrease, or one of the tablets will stick and become a such hit on the market to rival Apple’s device. Who knows: it could be the Kindle Fire one day.