Once it becomes plausible that any squirrel, mouse, dragon fly, etc. could be an assassination weapon, it will become necessary for heads of state to travel surrounded by swarms of friendly robots, in all sorts of form factors.
But I expect all of us will be surrounded by swarms of friendly robots some day, both to help us with tasks and for security (some kind of artificial immune system?).
As usual with war tech, the research will eventually find its way to consumer products.
Why? If you were a country, would you like to deal with a decentralized/unofficial government that has no control over its citizens?
Travel does not have to mean 'travel outside the country', so even if most attempts to decapitate a country are home-grown that doesn't mean that heads of state don't travel with a security entourage when they are within their own borders.
On top of that I do believe that heads of state already travel with a security entourage when traveling abroad.
It is not necessarily the other nations they're afraid of but their lunatics. And a small robot drone will be within the financial means of anybody with an axe to grind in the fairly near future.
also there's a cult centered around a subconsciousness born in a group sex ritual.
so yeah, good book.