I think we'll see a significant update with the next model. It would have been three years since the last major change, the introduction of the Retina display. Since then all we've got is spec bumps.
802.11n -> 802.11ac
Thunderbolt -> Thunderbolt 2
SATA SSD -> PCIe SSD
650m -> 750m
Iris -> Iris Pro
Ivy Bridge -> Haswell
There hasn't been a new feature. And when June 2015 rolls around that'll be 3 years exactly since the last major update.
I don't think we'll just get another GPU + CPU spec bump. I think we may see TouchID make its way over to the Mac and it would tie in well with a preview of the next version of OS X 10.11 which is expected to be shown at WWDC if they keep their cadance.
My prediction, Retina MacBook Pro refresh, perhaps even introduction of this MacBook Air Retina (Like they did in 2012's WWDC with a few hardware updates across the notebook lines). Then they'll show off a preview of 10.11 that uses the new TouchID sensor and some other general changes and a preview of iOS 9.
Admittedly I've been wrong before but this time I got a feeling!![]()
They might release it in Spacegray too... To keep it in line with their other mobile devices.
I'd love to see a on/off button with integrated TouchID. Place your finger on it, instant unlock, the same for buying things in the App/iTunes store or login in to various sites or Apps (think of your Mail, calendar, etc.)