I don’t think it will come back.
I couldn’t find the latest revision by Ton… dropped off my feed reader. Darn I need to create a history file I guess. I did find this reply by Ton in the bug report that caused the revision I remembered (disable animate feature in Relations / Layers, which was already broken by an earlier revision I suppose).
I never had problems with it but apparently some did. In the svn log Ton mentioned it causes difficulty for future dev, IIRC.
Ton’s replies in the bug report…
Layer animation is not supported, we will make the button disable this option now.
Instead, animate the visibility options in outliner.
The layer position is part of the dependency system for animation, if you animate it things become unpredictable or don’t update.
In your example you animate object layer, to replace this with ‘visible’ in outliner is not more work.
Realize that this option never worked, except for simple things without dependencies on other objects. If we offer a feature in blender, it shouldn’t fail that badly.