The 21.5-inch iMac, with 2.7 GHz i5 quad-core processor, currently for sale at the Apple Store is considered a 2013 model. It is still being sold as new in 2015. The 2014 21.5-inch is a 1.4 GHz, dual-core i5 processor, and has a different market, I think.
It's much the same as the 27-inch, non-retina iMac is still sold, but is actually a 2013 model. The retina iMac also has a different market - so you could say that there are currently 4 different iMac lines for sale.