Sales of tablet computing devices will double in 2011 to 24.1 million units, and keep climbing through 2015, according to a report issued today by Forrester Research.

"Of those sales, the lion's share will be iPads, and despite many would-be competitors that will be released at CES, we see Apple commanding the vast majority of the tablet market through 2012," analyst Sarah Rotman Epps said in a blog post today.

Epps said tablet buying will be more like sales of MP3 players or iPhones than PCs. They are primarily lifestyle devices that people will replace more frequently than computers.

In other words, we think a significant number of first-generation iPad buyers will buy iPad 2 when it comes out this year -- many first-gen iPads will end up entertaining the kids in the back of the car while Mom and Dad get the shiny new (likely Facetime-compatible) model.

As for Android tablets, Research In Motion's BlackBerry PlayBook, Microsoft's Windows-based tablets, and tablets that run on HP's and Nokia's platforms, they'll take a backseat to Apple, but in a market this big, there's room for more than one player. By 2015, 82 million US consumers -- one-third of US online consumers -- will be using a tablet, and not all of them will be iPads.

Here's a chart from her blog:

Here's another from her report, via Mary Jo Foley's blog, where I first saw the report: