Am 04.02.2016 um 08:03 schrieb Markus Krötzsch:
Data model updates are costly. Don't make them on a week's notice, without prior discussion, and without having any documentation ready to give to data users. It would also be good to announce breaking technical changes more prominently on wikidata-tech as well.
These have been discussed for months, if not years. Especially identifiers.
I do not consider adding new data types a breaking change. Converting existing properties to a different data type is a breaking change to the data-set, not to the model or the software.