isn't the reason io was formed because node was so outdated? It had a way old version of v8.
https://groups.google.com/forum/#!msg/v8-users/UUyavs0KtwE/d...
So this means that the branch is supported until Chrome 42 goes in to the stable channel. Though a case could be made that since 4.1.0.21 is tied to Chrome 41, which is still on the Beta channel, and "Our stability expectations are the same for every branch (once it starts shipping on Chrome stable, which is roughly 6 weeks after it's been created)"
[0] - https://github.com/iojs/io.js/blob/v1.x/CHANGELOG.md
[1] - https://chromium.googlesource.com/v8/v8.git/+/4.1.0.21