Haven't seen this published anywhere but I understand that as of 1 March:

Silver increases from 25% to 30% bonus miles
Gold increases from 50% to 75% bonus miles
Platinum increases from 75% to 100% bonus miles

applicable to tickets issued or resissued after 23 January 2023. Perhaps this is in response to negative feedback to the brutal Skywards devaluation.

Retaining platinum also now requires one qualifying flight in J/F. Doubt this affects many people as obtaining 150,000 tier miles flying only in Y would be some achievement...