Princess Anne could take on the royal responsibilities of Prince Harry and Prince Philip, according to reports.
It is believed the Queen will reward her only daughter, 70, with the honorary titles as she "commands the respect of the armed forces".
She is also considered the "hardest-working" member of the Royal Family, Thomas Mace-Archer-Mills said.
The founder of the British Monarchists Society added that she is married to the "military man" Vice Admiral Sir Timothy Laurence and her "no nonsense" attitude is "what the military is about", the Daily Star reports.
He told the Daily Star: "Princess Anne is very happy where she is: she's not one for fuss, just like her father.
"She's time after time considered the hardest working member of the Royal Family.
"It would be a shock if she was not at least given the opportunity to decline some of those patronages that have opened up.
"She is no nonsense, duty, to the point, she's not one for small talk, she tells it straight and that's what the military is about.
"Her very demeanour is very good for the patronages that her father had."
Prince Harry, who served in the Army and completed tours of Afghanistan, and his wife Meghan Markle were stripped of their royal patronages and military titles before their bombshell Oprah Winfrey interview in March.
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Prince Philip's titles and patronages were returned to the Queen on his death on April 9.
Since then, Princess Anne took centre stage as the Royal Family marked Anzac Day last Sunday.
She laid wreaths at a war memorial while Prince William, the Duke of Cambridge paid tribute to the "indomitable spirit and courage" of Australian and New Zealand forces.
Thomas Mace-Archer-Mills said it 'would be a shock' if Princess Anne weren't offered Harry and Philip's honorary titles
Mr Mace-Archer-Mills said: "She is constantly doing what's expected of the Crown and there's a very big difference between her work and her nephew Harry's, so she's going to be picking up a lot of work in the coming years because the Crown is down a player.
"There's a few that are open from the patronages that were returned to the Queen from Harry.
"Being the Queen's only daughter it really shows well that this woman who was not born to be King or Queen is the one to take these honorary patronages and make something of them.
"She commands the respect of the armed forces and that's why she will be given more of those honorary patronages which will have been left behind by Philip and her nephew chose to abandon."
