The phrase "it is highly likely that" is correct and usable in written English. You can use it when you are expressing an opinion or prediction about a situation having a high probability of occurring. For example: "It is highly likely that the new regulations will have a positive impact on the environment.".
It is highly likely that types of human-poultry contact differ between and even within countries.
It is highly likely that purchase will have brought BHV-1 into restocked herds.
It is highly likely that the foam-like biochar can trap some of the inorganic salt.
— Barash concludes that it is "highly likely" that religion owes its origin to natural selection.
It is highly likely that post-Brexit we post-British will too.
It is highly likely that proceeds from this racketeering have been used to finance the fighting.
It is highly likely that the attackers also came from many nations.
Ludwig does not simply clarify my doubts with English writing, it enlightens my writing with new possibilities
Simone Ivan Conte
Software Engineer at Adobe, UK