From Yes' Facebook page:
"Yes (official) YES Recruit New Singer Prog rock band YES were forced to cancel the last 3 shows of their European Tour in December due to the illness of lead vocalist Benoit David who has still not recovered. To avoid disappointing their fans on the forthcoming Australasian leg of their world tour, they have found a replacement singer. Jon Davison will join YES as lead vocalist for the upcoming dates in New Zealand, Australia, Japan, Indonesia, and Hawaii. YES really appreciate Jon Davison joining them for this leg of the tour and are sure this arrangement will satisfy all YES fans."
Talk about a revolving door! It doesn't pay to fall ill if you're a member of Yes.
Nevertheless, best wishes to Jon Davison! I love his (former, I guess) band, Glass Hammer.