I think Duokan for PW2 is released :
http://bbs.xiaomi.cn/thread-8955274-1-1.html
I'll test it in 20-30 minutes and give my feedbacks here.
Edit : Paperwhite 2 5.4.2 bought on Amazon France.
Install is so easy... no problem for the moment, and have a lot of pleasure to use this release
Edit2 : For me, this Duokan is much faster than original OS. And i love to add fonts easily and play with numbers of settings. There are many languages available like English, Russian, Chinese. Looks like it's stable for the moment.