What about phrases like “totally certain” or “almost certain” or “probably certain” (or “certainly probable”) and the like?
In another nearby thread, Skald the Rhymer’s eccentric billionaire offers YA dare for $500,000. drewtwo99 is either certainly probable or probably certain to take him up on it, but only probably so (but at least he’s sure of that). 
(ETA: Upon re-reading, that is, if Eccentric Billionaire is open to negotiating the purse.)
Is “sure I’d probably” oxymoronic or (since others have nitpicked the meaning of “oxymoron”) otherwise improbable?