Okay, I’ve seen several students making mistakes on the use of these two words. Let me make the difference clear.
UPCOMING refers to “Something which is about to take place”.
You can’t say “In the upcoming years”
Why? Since the YEARS are not about to take place. Note that years are NOT something.
But you can comfortably say “The upcoming meeting is about Brexit.”
“The agenda for the upcoming conference is reviving agriculture in India.”
Upcoming is used with something. It is NOT used with TIME.
“The coming years will be harsh for humanity if the threat of global warming is not addressed.”
You can use coming with time.