Willis, 32, who was diagnosed with cancer in December, had already qualified for Rio in the 470 with Luke Patience, but the British pair have been withdrawn.
"The thoughts of all the team continue to be with Elliot in his ongoing recovery," Patience said.
Five have been added to the squad for Rio, including windsurfer Nick Dempsey.
He will compete at his fifth Games while Charlotte Dobson and Sophie Ainsworth will make their Olympic debuts in the 49erFX.
European 2015 champions Ben Saxton and Nicola Groves have been selected for the Nacra 17.
Patience, a 470 silver medallist at London 2012 with Stuart Bithell, will attempt to re-qualify with Chris Grube.
The decision to withdraw Willis and Patience was taken by the British Olympic Association and Royal Yachting Association (RYA).
"Hopefully this doesn't mark the end of Elliot's Olympic journey and we look forward to seeing him back in the boat soon," RYA Olympic manager Stephen Park said.
Full squad:
Giles Scott, Finn
Nick Thompson, Laser
Alison Young, Laser Radial
Hannah Mills and Saskia Clark, 470 women
Charlotte Dobson and Sophie Ainsworth: 49erFX
Ben Saxton and Nicola Groves, Nacra 17
Bryony Shaw, RS:X women
Nick Dempsey, RS:X men
Two-time world champion Elliot Willis will miss this year's Olympics because of his treatment for bowel cancer.