The Swiss National Bank (SNB) has issued a speech transcription in which the speaker mentions that the new 20-francs banknote will be unveiled on 10 May 2017 and the new note will be issued to the public on 17 May 2017. From earlier reports we know that the new 20-francs note will be red and have Light as its main theme.
Issuance of the third denomination, the 10-franc note, is planned for autumn 2017. The exact date will be announced in due course. The 10-francs note will be yellow and have Time as its theme.