There are some places in the CLI codebase where we should synchronise code execution (due to Node.js single-threaded, async nature), certain operations needing to be run only after others are done. This can be achieved either with callbacks or better with ES6 (latest Javascript) Promises.
Also check if latest Node.js supports ES6 natively or if we need to use a polyfill library like bluebird

First evaluate, and estimate how much work it would be to switch to promises. Discuss with PXM, and we'll decide whether to keep in v 3 release or postpone.