We will need a time period, after some announcement, for people to test the new geo-shapes data type (e.g. on test.wikidata) and for people to adapt their tools (e.g. pywikibot, wikidata toolkit).

Also, we would want wikipedias to be able to handle geo-shapes soon as it is enabled, even though they don't get new code the same day as Wikidata. Best way is to have the code there one deployment cycle before enabling new data type.

See also: https://www.wikidata.org/wiki/Wikidata:Stable_Interface_Policy