To describe a person as "forthcoming" in that sense* sounds a bit odd; it is usually applied to a period.
'Upcoming' is a back-formation from 'coming up'. Not many Br English speakers use it - though this may well not be true of Am E speakers. In Br English, we usually describe a newly-elected presiden as incoming.
*There is another sense of 'forthcoming' which applies (exclusively, I think - although I suppose some people might apply it anthropomorphically to animals too) to people. In this sense, it means 'willing to share their thoughts/not shy/open'.
Interestingly, in the area of presidents taking/leaving office, the word 'retiring' also has a meaning almost exactly opposite to 'forthcoming'. Hence the old joke 'The retiring President didn't want his photograph taken' (copyright Clive Anderson 1975 - BBC - Radio 4 - Presenter - Clive Anderson - but knowing him [as a fellow writer/performer at the time] I wouldn't be surprised if it wasn't original even then).
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