ICAO SARPS state:
It is to be noted that in the English text the following practice has been adhered to when writing the specifications: Standards employ the operative verb “shall”, while Recommended Practices employ the operative verb “should”.
There is no mention of 'will' in ICAO SARPS notes, therefore it could be assumed it is only a descriptive term and has no formal status. ICAO altimeter setting SARPS may indicate exactly what ICAO desire, with appropriate differences filed by countries (such as the UK) who do it differently