Stick a fork in them, they're done. In the post linked in the title from AutoBlog, Ford has decided not to continue the Mercury Sable. They've made a load of changes to the Taurus, including a new SHO, but no plans for a 2010 Sable.
This leaves Mercury with only 4 models, 2 of which will end production soon. The Milan, which is an upscale Fusion, the Mariner which is an upscale Escape, the Mountaineer which I forgot they still made! And the Grand Marquis, which like the Crown Victoria and Town Car is dead man walking. So, with only 2 real models I'd say you can kiss Mercury goodbye. Autoblog mentions plans for an unnamed small car in the future, which can only mean an upscale Focus, even thought they mention the Lincoln C concept.
If Ford wants to keep the Mercury brand alive and at this point that seems unlikely, they need new models to keep the brand. I had said over the years that Mercury would be the perfect brand to bring the neat European and Global Ford products to the states, but since, the Fiesta and new Global Focus are coming here as Fords, that shoots that down. It would be nice to dream about the Australian Ford Falcons coming as Mercury models, but that's unlikely.
So, why keep the brand? It used to be a nice filler between Ford and Lincoln, but as some Fords approach Lincoln prices and Lincoln has their "entry" level MKZ, there's no filler needed.
Mercury will be gone in as little as 5 years, but no longer than 10, unless FoMoCo comes up with something fairly snazzy and profitable for the brand. But look at the bright side, now those who want an orphan car like and Edsel or Studabaker can get a fairly modern vehicle to bring to shows. Hell, the way brands are being killed lately, orphan car shows are going to be loaded with late model iron. I wonder if I should start checking e-Bay for a 2003 Marauder?