Is it obligatory to repeat the Hajj for someone who intended to repeat it due to the possibility of nullifying their ablution during the Farewell Tawaf, even if they do not currently intend to repeat it but hope to do so in the future?

Whoever performs the obligatory act as required by Sharia (definition) has fulfilled their duty and is not obliged to repeat it. Repeating an act of worship without a valid, Sharia-approved reason is impermissible and might even be prohibited, especially repeating a doubt without cause. The farewell circumambulation (Tawaf (definition) al-Wada') is not a pillar of Hajj, so whoever omits it, their Hajj is valid, but a sacrifice (dam) becomes obligatory according to the majority of scholars. If you began the circumambulation in a state of purity and then doubted whether your ablution was broken, it does not matter, because certainty is not removed by doubt. If she constantly suffers from discharges, then she is considered like someone with incontinence (sahib al-salas), and her circumambulation is valid. One should beware of obsessive whispers (waswas).