I believe that GMC is replacing the Envoy with the 2010 Terrain.
Here is a link to it on there website: http://www.gmc.com/terrain/terrain/index.jsp?pvideo=false
This is GMC just basicly renaming there midsize SUV/Crossover offering. The Envoy replaced the Jimmy almost a decade ago. Now the Terrain will replace the Envoy.
If you had to settle for something, the Acadia would be less of a jump then a Yukon/Yukon Denali. I have a 2008 Yukon Denali and it is much larger than an Envoy and more imposing than an Acadia.