JC-
Probably so, LHO eventually would have been captured, although in the 1960s-era, anyone with a valid-looking passport could leave the country, even through US ports. No computer connections.
Could LHO, with a bleached Fu Manchu and hair, some elevator shoes, and a "valid" passport, leave the US, say after six months or a year?
James "Whitey" Bulger (16 years on the lam): The South Boston organized crime boss went into hiding in 1994 to avoid racketeering and murder charges. He was on the FBI's Most-Wanted list for 10 years, and a $2 million reward was offered—one of the highest for a domestic target—before he was finally captured in Santa Monica, California, in 2011.
But, as you say, LHO's behavior on 11.22 was inexplicable.