Is expiation (kaffarah) obligatory, or only repentance, for someone who deliberately swore a false oath that something future would happen, knowing that neither that thing nor what the oath was contingent upon would occur? And is this considered a Yamin Ghamus (a deliberately false oath concerning the past or present) or a Yamin Mun’aqidah (a deliberate oath concerning a future action)?

Your oath is not a ghamus (perjury) oath; rather, it is a mun‘aqidah (binding) oath, because it pertains to a future matter that could occur. If the matter upon which you swore the oath does not materialize, then you owe an expiation for breaking an oath (kaffarat yameen). Oaths are of four types: a mun‘aqidah (binding) oath, which necessitates expiation if broken; a laghw (idle) oath, for which there is no expiation; a ghamus (perjury) oath, for which there is no expiation according to the majority of scholars, though it may be obligatory according to Imam Ahmad; and an oath concerning an impossible matter, for which there is no expiation.