you can say 'hayırlı olsun' or 'mutluluklar dilerim' I guess. first one sounds more like something a muslim would say.
also some people say 'allah bir yastıkta kocatsın' or 'bir yastıkta kocayın'. it means 'I hope you get old together'. (word to word it means 'get old on a single pillow'. there was long pillows which could be used by two people in the past, I guess my parents still have one at home but I dont know where it is, they dont use it. I wouldnt use as well, its hard as rock lol)