Other than better performance than Node.js 0.12, will any codebase in Meteor.js to migrate to ES6?
Meteor 1.2 will have built in support for ES2015 -> Public release candidate of Meteor 1.2
Apart from that I also wonder if the nodejs update will have any impact on meteor in the future?
The Accounts package on the devel branch is using ES6 things
I mean will the Meteor core code based completely revamp with ES6 syntax?
Most likely not. In open source projects with many people working side by side (and the same for closed source projects) you really want to avoid touching and changing more code and files than necessary since that would block a lot of work that could otherwise go on in parallel.
Plus when a project has a large code base you really want to avoid changing parts unnecessarily because that introduces risk that you will break something that has been working before.
As such I’m fairly certain that over time the Meteor code base itself will move more and more to ES6/ES2015 and the language standards that will come after. But it will be a gradual shift, happening over time as each piece of code is touched and gets its ES20XX overhaul.
And the topics of ES6 and Nodejs v4 are really different topics. At some point Meteor is going to move to running on Node 4.x by default, and that itself will provide some ES6/ES20xx features natively, but fundamentally all of the new language features are available to us anyway already and so the question of which version of Node Meteor is running on / deployed on is not that important from a “which language features can I use?” perspective.