Hmm, seems they gave S40 some love recently:
http://www.wechat.com/en/S40_1_0.html

If someone is gifted enough, they could figure out how it works and try and get an N9 version going. From memory, this is how tgalal worked on the initial version of wazapp and how people learnt how it worked (along with the knowledge it works with xmpp).