Legacy devices means devices from 3-4 years ago for Apple. If I buy a Windows phone today, it won't run the next major version of the OS. I'm just glad I didn't buy a Lumia 900 when my upgrade became available like I planned to.
My original iPad is now legacy barely more than 2 years after it's release. It's last available update is from June 6, 2011. So essentially about 1 year and 2 months of support.
