It's not 7 species, but how many players is it ? You said right from the get go that races were customisable (which is very standard for the genre) so their number was never a worry, but what Grand Strategy should bring is a great number of entities not necessarily vying for any kind of "victory". All of your historical games have had dozens and dozens of nations even in their blobbier moments, with CK2 taking the cake with hundreds of more-or-less autonomous landholders.
With the move back to a more traditional 4X model, the "symmetrical start" from a single planet and the single screenshot of the political map from your steam store page, I've been led to believe that this won't be the case for this game. I'd love to be wrong and learn that new nations will pop up by the dozen in the mid-game because of separatist tendencies or other civilisation discovering interstellar travel later than the starting few, but in that case : Let us play as them. Plenty of playing with backwards nations has been done in the EU and Vicky series, I'm sure the experience could be interesting in space too.
They already said there will be many and many smaller factions you can meet in your game. You can even meet species without space-traveling and observe them from their moon.