The dramaturge does state that the two Viera clans are Rava and Veena, so it's all but confirmed that these will be the two clans. And from what we've seen, we can expect them to be palette swaps of each other with a few minor differences; this is the case for most of the current playable races. And it's important to remember that Rava and Veena are not new concepts. The idea of Rava and Veena has been around for years. Although admittedly, I am not familiar with the specific lore for Rava and Veena.
If there is going to be a "young-Elezen looking" variant, as Namae stated, how will they be implemented? Will the short variants be one of the aforementioned clans, or will they be treated as a separate race, the way Feol is treated separately from Viera? Maybe the short variants are supposed to be a stand-in for Feol.
The short variants we see in the concept art do share some visual similarities with Feol, such as shorter ears and smaller stature. In a way, we'd be able to play as Feol, but with another name. To quote Shakespeare again, "A rose by any other name would smell as sweet." This might lead us to something like this.
Unless both Rava and Veena are of the tall variant, and they create another race for shorter Viera. But this seems extremely unlikely. I doubt this will happen. If the tall and short variants are treated as separate races, and not just clans, that means there will be a total of four new clans, instead of just two. My guess is that the tall and short variants will be divided into Rava and Veena, respectively.
But this is assuming that we will even get playable short Viera.
The wandering dramaturge didn't mention any other differences between Rava and Veena other than skin tone. So this could all be ruled out. And we might be reading too much into Namae's comment of a "young-Elezen looking" variant. Perhaps she was just referring to hairstyles or facial shapes. But then again, Yoshida and the others seemed quick to tell her to not talk more about it. It seems there is more left to reveal about Viera.
The only thing we know for sure is that we are getting the tall variant of female Viera, which is the category Fran falls into. They have similar builds as female Elezen: relatively broad shoulders, long necks, and long limbs. To compare, I posted some pics of my female Elezen alt.
It seems that these female Viera will be around the same height as female Elezen. To get an idea of how tall they may be, here is my max-height Elezen main standing next to Fran. I also took pictures of him standing next to the company belle, the wandering dramaturge's wife (does Matsuno like tall girls?)
I'm not sure where Fran is on the height scale. She could be max, average, or minimum height. But either way, these female Viera are going to be tall. They're definitely going to be taller than the petit catgirls and dragongirls that dominate the current population. And that's something I do appreciate.
I just wish that whatever we get for males is an actual equivalent to the female Viera we see now. I'm going to be so disappointed if they go with a conventionally attractive female race, and a beast-like male race.