The review of SE-0034 "Replacing Equal Signs with Colons For Attribute Arguments" ran from Mar 2…4, 2016. The proposal has been *accepted*:
The community and core team uniformly agree that this proposal increases uniformity in the swift language.
Contributor Daniel Duan is (again!) way ahead of the game here and has already submitted a pull request (https://github.com/apple/swift/pull/1537) to implement this improvement.
Thank you to Erica Sadun for driving this forward, and Daniel Duan for working on an implementation of this change!