DeferredCommand has been deprecated since Scheduler was added. Patrick Tucker submitted a bunch of patches to remove those uses of a deprecated API.
This is not something coming from Google, so don't see a sign or anything behind it, it's coming from an external contributor.
Be prepared though that a bunch of deprecated APIs will probably be removed in the next months, in order to clean-up the code base: event listeners, com.google.gwt.event (with a breaking change in Activities), many c.g.g.u.c.DOM methods, etc. SO if you're still using DeferredCommands, you should probably start slowly moving them to Scheduler.