I never heard or seen anyone who seriously argued that IntelliJ and Grade should destroy Eclipse and XML (what has one to do with the other anyway?). And even if somebody actually thinks so you are better of avoiding them because they did not understand what they where taking about. Eclipse, IntelliJ, Maven and Gradle are all tools that have specific advantages and disadvantages compared to each other, and determining what tool is best for a task depends from a lot of things including your personal experience. That said, there is of course a Gradle integration for eclipse. See here, first point.
For the dependencies, I am not aware of any official announcement expect that Forge’s libraries will available at runtime, see here.