Sadly, yes, Destiny 2 Monument of Triumph will be the last content update. This means that Destiny 2 has ended live-service support, so don't expect changes to the meta. There will be no more additional weapons/gear, expansions, or seasonal events. Destiny 2 will essentially be frozen in a legacy state like the original Destiny.
What Content is Getting Added with Monument of Triumph?
Monument of Triumph conclusion mission
Legendary Marks
New Reward Pass
Pantheon 2.0
Sparrow Racing League
Vanguard Ops
Crucible Ops
Armor 3.0 for Raids, Dungeons, and Destinations
No, Destiny 2 is not shutting down with Monument of Triumph. The update is the last content update, but there will still be occasional bug fixes and maintenance required to keep the game running. You will still be able to play Destiny 2 for years to come.