Are we close to knowing the plant diversity of the Amazon?

Amazonia is often cited as having the most diverse flora on the planet. However, the total number of species of higher plants in the region has been largely a matter of guesswork. Some recent publications have estimated the total number of species present, which indicate a lower overall diversity than was estimated in the past. However, analysis of the sampling density across the region, and data from various sources suggest that there may be reason why the recent figures may be considerable underestimates. I believe that much more investment in extensive collecting of quality plant specimens is needed to encounter the very large number of rare and local species that might never have been collected. Unfortunately the tendencies of investment in botany, in terms of geography and types of project, suggest that we will probably not be able to accurately assess the real diversity of the region.