forthcoming vs coming

forthcoming is not a noun while coming is a noun.

Word	Noun	Adjective	Verb	Adverb
forthcoming	No	Yes	No	No
coming	Yes	Yes	No	No

As adjectives, forthcoming and coming are synonyms defined as:

Other synonyms of forthcoming include approaching, upcoming.

forthcoming (noun)	coming (noun)
	the moment of most intense pleasure in sexual intercourse
	arrival that has been awaited (especially of something momentous)
	the act of drawing spatially closer to something
	the temporal property of becoming nearer in time

forthcoming (adjective)	coming (adjective)
available when required or as promised	of the relatively near future
of the relatively near future
at ease in talking to others