Breaking backwards compatibility is a more apt description of that list than major rewrite.
Part of the lesson from Python 3 is that large numbers of people will only spend 3 years deciding whether a 5 year plan to make a major change to a 20 year old language succeeded or not.
Agreed. If there's one thing that Bill Gates understood better than everyone else (with the exception of maybe Intel) is that you never break backwards compatibility. You have instantly leveled the playing field for all of your competitors. Why should your users use YOUR new language if there are other languages that already exist and they are just as incompatible as your language?
It's not as simple as that. Eventually continued backwards compatibility hacks will cause non-negligible problems, and some of those same customers may start viewing the competition differently when they finally decide to rewrite or choose a new system to replace their aging one. It's a fine line.
> we shouldn't attempt major changes that aren't backwards compatible?
I think is more about practicality. Incompatible releases are a huge hassle for users; the payout should be equally huge to make it worth the effort of porting.
As the post says, a language should try to be the best choice for new projects: easier and more powerful than other choices, delivering better results with less effort. An incompatible release starts from a position where it requires more effort, so it must deliver much better results in much less time or it will be discarded on practical ground (and all the while having the same feel and strengths as previous releases - you can't make Go, call it Python 4 and expect people will love it). That's very difficult to deliver.
I guess we should learn to design languages with extensibility in mind from the outset, so that later incompatible changes are much less likely to be necessary.
Part of the lesson from Python 3 is that large numbers of people will only spend 3 years deciding whether a 5 year plan to make a major change to a 20 year old language succeeded or not.