要是我，我会这样说：Dear Mr./Mrs. ...： You know you have made great contribution to the company, and made us more like a team.We are happy to work with you,and learn much from you. Thank you very much. We will miss you.仅供参照。（我觉得还是当事人表达比较好，不管说得怎么样，真情实意更重要）
Thanks for your years' contribution and dedication, and wish you a happy retired life! 如果是作为BOSS的话。。但是平级的话嘛，卡片就Congratulate your retirement and enjoy your retired life! 这样就差不多了吧？嘛，更省力不用自己编的方法呢，就是在google.com 里用关键词 cards for retirement搜索，就能出来很多网站有电子的贺卡啊，还有贺卡定制啊，都能看见外国人各种搞笑的正经的卡片说法，毕竟这边流行干啥都送张卡片233333 这边给出一个我搜出来的结果做参考~Hope it helps :)额，才看见LZ在另一个回答下面补充的，奖杯上的话，还是 To honor Mr/Ms XXX for decades(如果工作数十年)/years(过过没有数十年) of contribution to the firm. Wish you a happy retired life! 或者Thank for Mr/Ms XXX for XX years of great service. 之类之类我不确定wish you a happy retired life 作为刻在正式的奖杯上适不适合，LZ自己判断下吧:)
末日女友CCCccC
