Those factors were certainly important, but keep in mind the level of detail here--certainly, in a comprehensive history class, they should be at least alluded to. However, i doubt that Henry the Navigator was influenced by the fall of the vestige of the Roman Empire to the Turks, as it occurred in 1453, and Henry's interest likely dates to his father's capture of Ceuta in Morrocco in 1415--almost 40 years before the fall of Constantinople.
I left North America out the picture, too, even though European fishermen, whalers and seal hunters had been going there for centuries. However, they generally weren't telling anyone else, because they didn't want any competition for resources. I'm sure the Portuguese tried to keep their sudden new sources of gold dust and ivory, and, eventually, of spices, a secret, too. But when you suddenly have lots of valuable items to sell, at discount prices the Italians can't been, and are getting rich off of it, the cat is out of the bag by then anyway.