Last week the Node.js Foundation released Node.js v6. Node.js v4 is still the only Active LTS version. Until v6 becomes Active LTS in October 2016 it is Current (like Node.js v5) and recommened only if you want to play with the latest features. If you need stability you should stay on v4.
See their announcement and LTS Release Schedule for details.
Of course we want to be ready for Node.js v6 as soon as we can. Currently there are two known issues which we plan to resolve for the 5.4 release in June.
- CLI-999 fs: re-evaluating native module sources is not supported
- TIMOB-23285 Unable to build for Android and iOS
If you feel adventurous and run into other issues after upgrading to Node.js v6 please report them on JIRA.
Continue to use the latest Node.js v4 for Appcelerator development until we announce support for v6, which should be ahead of it becoming the Active LTS version.