IDC has just released their second quarter results for tablet and eReader shipments as well as an updated forecast for the remainder of 2011. While Apple continued to dominate with 68.3% of the global market during Q2, IDC expects Apple’s share to fall as vendors bring competitive Android devices to market later this year and early next.

The study reports second quarter tablet shipments worldwide increased 88.9% (303.8% year over year) citing robust demand for the iPad 2 and sales of 9.3 million units, leading the firm to raise its estimates for the remainder of 2011 from 53.5 million units to 62.5 million.

From the report:

Android suffered a blow to its market share during the second quarter, slipping from 34.0% to 26.8%. IDC expects Android’s market share to drop again to 23% during Q3, before increasing to 25.9% in Q4 as vendors introduce new Android-powered competitors.

IDC reports RIM was able to grab 4.9% of the tablet market in 2011 with the introduction of their BlackBerry PlayBook. The report cites the PlayBook and iPad as the main factor for Android’s decreased market share, but with approximately 1 PlayBook to every 19 iPads shipped, we know it’s a lot more iPad and a lot less PlayBook.

An influx of $99 TouchPads (close to a million) will increase market share for WebOS to 4.7% by Q3. However, that share is obviously expected to be zero come Q1 2012 as vendors cease licensing the OS.

Cross-posted on 9to5Google.com