in 2.4 we will use PARAM_TEXT to describe the Moodle version numbers in core_webservice_get_site_info() - see MDL-35593. Version numbers were previously declared as float. It was an issue because the Moodle version numbers are too big to be a float on 32 bits processors.
I think the change would break clients that are auto generated like the Java/.Net clients using SOAP. Till now it was not a problem because we could not generate these kind of clients as Moodle WSDL were not compatible. However some work have been done recently on the subject - see MDL-28988.
I still think it's a good time to backport it before many people can auto-generate clients. How many of you would be impacted by this fix?