[maxerickson]

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.

[hvs]

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?

[kbenson]

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.