They should read: 1) The meeting is being held on the/this coming Monday. 2) The meeting is being held on the/this upcoming Monday. Upcoming warns readers that the event is near.
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Upcoming is wrong. It refers to "Something which is about to take place." Monday is not about to taking place.
Correct sentence using upcoming: "The upcoming meeting is about Brexit and its impact."
"The upcoming conference's agenda is to revive agriculture in Britain."
Hope this helps!