Yes, I noticed this and even asked a question about Spring use of Gradle in March 2010 on Gradle dev lists and got the following answer from Luke Taylor:

"We are still using Maven as the official build tool, but I've been maintaining an experimental gradle build in parallel for some time. One of the sticking points was generating maven poms with the correct dependency information, but that is now possible with the latest 0.9 snapshots. Hans has helped a lot with suggestions and refactoring so the build is looking pretty good. AspectJ support is the next thing on the agenda."

I don't know if they have any plans for replacing Maven with Gradle.

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Tomek