I couldn't find any discussion related to that and I've been told core contributors aren't a fan of promises but I thought I'd kick start a discussion anyway. I had assumed this was discussed at length already but couldn't find any relevant links.

The proposal would be to make all async methods of the core library return promises. This could be done in a backwards compatible way by using something like bluebird's nodeify (now asCallback) which would allow both errback / promise styles to co-exist.