Are Hugo Chavez' days numbered?

Yes, but then again so are everyone's.  However, Chavez might have fewer than most. From Fausta:

After returning from his latest round of chemotherapy in Cuba, Venezuelan dictator Hugo Chavez is hospitalized with renal failure and medullary aplasia:
The UK’s Telegraph reports, Hugo Chavez in hospital ‘for kidney failure’
Hugo Chavez, who has been fighting cancer, was rushed to a military hospital for emergency care following kidney failure, according to reports.
El Nuevo Herald also reports that (my translation: if you use this translation please link to this post and credit me):

On the other hand, the source stated that Chavez suffered from medullary aplasia, the disappearance of blood-producing cells in the bone marrow, which complicated his medical state. According to doctors, medullary aplasia can be total, affecting the production of red and white blood cells, or partial, which affects the production of one type of blood cells.

He closes with this:

Ambassador Roger Noriega last week was saying “we must start thinking about, and preparing for, a world without Hugo Chavez.”

Indeed.