I think there are celebrations planned around the 80th anniversary of the end of WW2 that will require a royal presence. And given the gov now appear desperate to regain the speshal relationship with Trump, I wouldn't be completely surprised if an invitation, possibly coinciding with a state visit was forthcoming.
We can play spot which Royal has the best fake smile. My money is on Camilla being the first one to get her excuses in for not going and I'll go for an accumulater on a convenient chest infection.