Handre Pollard has agreed to join Top 14 heavyweights Montpellier and Morne Steyn will return to his homeland to replace the fly-half.
Franco Smith has accepted the opportunity to coach at international level with perennial Six Nations strugglers Italy.
There will be three Du Preez brothers - including twins - and identical Curry twins at Sale Sharks next season.
The Dragons believe ex-Gloucester and Worcester Warriors boss Dean Ryan is the right man to turn around their fortunes as sporting director.