Relapse, or going back to an earlier stage, is extremely likely.

He might be held against his will, in fact it would be extremely likely.

He was considered extremely likely to make the Olympic team.

"I should think it extremely likely that they are still in Algeria."

"It seems extremely likely that their respect turns on exactly such a decision."

"But these are women extremely likely to take the steps necessary to live that fantasy."

I think it extremely likely that they will be.

It is extremely likely that these are one and the same.

Greek people are extremely likely to vote "No" even if that is not a certainty yet.

That the evidence is there, however, makes it extremely likely.