Yep, the building of web assets (transpilation, bundling, Sass compilation, etc.) has been removed from the CLI in favor of using gulp tasks, more here: ATTENTION: Upcoming Ionic 2 Starter Changes.
The only config file you’ll need for both v1 and v2 projects with the 2.0 version of the CLI is ionic.config.json, which is ionic.project with a new name and some of the properties will be changing 