The main reason for the new series is that the first euro banknotes were issued over 11 years ago and the technology in those banknotes is more than 15 years old. Even though the number of counterfeits is relatively low, it is important to maintain trust in euro banknotes and to stay ahead of developments.
So on 2 May we are  BIS central bankers’ speeches  3  launching the € banknote as the first denomination of the new series. The other denominations will follow in ascending order in the next few years.