More broadly, I think there’s a tendency to feel that “Scala 3 is our chance to get in all the breaking changes so that we can avoid doing breaking changes too often.” I think that’s wrong. The need to have a strategy for evolving the language without leaving people behind should really be orthogonal to Dotty. Dotty/Scala 3 is primarily about changes to the underlying calculus. To the extent that any language change may affect that, it’s necessarily to design that change in tandem with releasing Dotty. In my opinion, any change that without doubt does not affect the premise of Dotty, should be pushed off to 3.1. We should get 3.0 released as soon as possible (but no sooner of course), and once it’s released work on getting 3.1 released as soon as possible.
A major side benefit of this approach is greatly mitigating the fears that abound, that Dotty will be a python-3-esque community split.
In that light I would agree with deferring XML deprecation. (Of course, then certain people will start saying it will never really happen. But that’s the lesser of the two evils. We should definitely prove them wrong, of course…)