When will Apple refresh the new macbook air/ pro？

Now lots of people are talking about MacBook Pro on line and rumors are around that MacBook will be refreshed on WWDC 2015. Well, I think the date will be a little earlier than WWDC. We all know that Apple's products have a refresh rate, such as iPhone, iPad or MacBook.

1. About Refreshing Rate.
On June 12th, 2012, MacBook Pro with retina was first released; with CPU of Ivy bridge structure. But only the 15-inch models are equped with Retina Display.
On February 13th 2013, retina MacBook Pro was refreshed again, hardware upgraded and price cut. For example MD212, 2.5GHz dual-core i5 CPU, 8G DDR3L memory, 128G SSD.
On October 23th, when iPad Air was released, Macbook Pro was refreshed as well. CPU was upgraded to Haswell, and display upgraded to Iris.
The latest refresh of MacBook pro was on July 2014, CPU and memory upgraded. X72's memory was increased from 4G to 8G, while XA2 from 8G to 16G.
So, according to the information above, macbook Pro's refresh cycle was about 8 to 9 months.

2. The Date
Why between February and April?
Apple watch will be released in the first qurter of 2015 and on market in April. There are rumors that the conference will be 2.24. March or April is also possible. Maybe Apple Watch, MacBook Pro & Air will all get released or refreshed together. It seems to match the upgrade circle of MacBook pro.

Because of the delay of Intel's fifth core Broadwell, Apple just upgraded MacBook Pro slightly in 2014. Now that Broadwell has been released on CES 2015, so it won't be long before Apple equip it on the new MacBook Pro.

About Macbook Air Retina.
Apple is reportedly planning to release a new MacBook Air on Feb. 24, according to the Czech Apple news blog Letemsvetemapplem.eu
Just like year, this is expected to be a minor refresh for the MacBook Air family, with the 12-inch model not expected to be launched at the same time. Specific details on the kind of minor updates expected for this new MacBook Air refresh aren't available, though Apple should make use of newer, faster Intel chips for the 2015 models.
Rumors have suggested that Apple will launch an all-new 12-inch MacBook Air with a thinner chassis this quarter, which concludes at the end of March. A late February event could set Apple up to debut the new MacBook Air within that timeframe.
It's expected that the redesigned MacBook Air will sport a high-resolution 12-inch Retina display. There have also been claims that the device will feature the new, smaller, reversible USB 3.0 port.