:The Clarence House press release is cited in the article. Regarding the additional sources you have provided, the only one that probably could be used here is the first one and it doesn't change anything: 
 #BBC: "The alternative is for the palace to dust off a long-defunct royal dukedom (Albany, Connaught, Clarence, and Cambridge are among the vacant ones), and William and Catherine would become the Duke and Duchess of somewhere." 
 #Hello (WP:PUS): "This is her 'occupation' or 'job description', and does not mean she should be addressed as Princess." 
 #Mirror (WP:PUS): "She generally sticks to Duchess of Cambridge for royal engagements. But sources say she was probably listed as princess on the birth certificate because it is the more senior title." (BTW I understand Duchess is the more senior title). 
 #Hollywood.com (WP:PUS): "Last night, it was revealed that the Queen gave both Prince William and Kate new titles: Duke of Cambridge and Duchess of Cambridge. Kate can additionally be called HRH Princess William of Wales, or HRH Catherine of Wales." 
 #Twitter (self-published so not allowed for this purpose, see WP:TWITTER)