In my opinion the number of species is difficult to forecast. In a wet region as the Amazon forest, the Brazilian Pantanal, the Everglades in Florida, and mangroves for example, the possibility of discovering new species is a fact, Furthermore we can think in continents as the The African tropical rain forest, South West Asia countries and islands  where animals are feeding seeds. Near sources of water the dispersion may be through the rivers, springs and so on. Otherwise, many species has been destroyed by deforestation around the word.

You could find some answers pieces in: Tweddle et al., 2003. Ecological aspects of seed desiccation sensitivity. Journal of Ecology. 91, 294–304