I would be somewhat worried that this might break something like numpy (though not numpy specifically) which might be counting on the ability to write a wrapper that overloads this behavior.

Another concern is that people could be playing it fast-and-loose with actual types, and are returning something that fits the bill for a collections.abc.Sequence with length 2 (e.g. return [a, b]) but isn't an actual Tuple.

I would at least think that this should go through a deprecation cycle.