Can we make a list, that people can add/correct and copy/paste in a new message? This is the situation as i understand it for the moment. I'm not sure if all the Tour guys have confirmed for Vuelta, or if this is just a general assumption in most cases.
Tour: Bernal, Froome, Thomas, Roglic, Kruijswijk, Dumoulin, Mollema, Pogacar, Higuita, Lopez, Mas, Valverde, Quintana, Uran, Formolo, Pinot, Bardet, Aru, Landa, Buchmann, Woods
Giro: Nibali, Carapaz, Carthy, G. Bennett, Fuglsang, Evenepoel, Knox, Soler, Kelderman, Ciccone, Zakarin, Majka
Vuelta: Valverde, Mas
What about: Yates x2, Costa, Kämna, CF Hagen, Hart, Sosa, Sivakov, Nieve, O'Connor, Dunbar, Madouas, Martinez...
Im fairly sure Kelderman has said not so long ago he wanted to do the Tour/Vuelta double instead of the Giro, which also makes perfect sense for him and also lets him ride the Ardennes.