[oleganza]

If people have real compatibility problem to migrate to Python 3, harsh policies will do nothing about that. If I'm forced to rewrite my app I may as well rewrite it in Ruby, Go, Java, or whatever. Especially, if Python developers will prove to be aggressive about compatibility. Why would I migrate to Python 3, just to be forced to rewrite everything in Python 4 next time?

[maxerickson]

Well, you can sort of assume that they learned their lesson.

There also isn't really anything as drastic as the bytes/strings/Unicodes left to change.

(But these are better answers to worries about Python3 than they are answers to porting 2.x code bases)