Hey so right now this is a real issue - it’s not clear which parts of Meteor are part of the “future”, and which are from the past. (for example, I’d say allow/deny is on its way out)
To that end, we’re working on a pretty big project, the Meteor Guide: https://github.com/meteor/guide
The idea is, if you build you app according to those recommendations, we’ll take extra care to make sure you’re happy with new versions of Meteor. You can see what we’re thinking about right now by browsing the outlines in the
outlines/ directory of the repo and reading the issue threads.
I know that doesn’t help you at the moment, so as a core developer I can say that we have historically taken great care to maintain backwards compatibility and easy transitions as much as possible with new versions of Meteor. It’s bad for everyone if current users can’t easily transition to new stuff, since we don’t want to maintain old versions if we can help it.