The old passports are valid until their expiration date:
http://www.bmi.bund.de/SharedDocs/FAQs/DE/Themen/Sicherheit/biometrie_faq_gueltigkeit.htmlHowever this doesn't solve certain things. Another country might not accept it.
Example: it is mandatory for German citizen to get a machine-readable passport to enter USA territories, even though Germany says above old passports are valid until their expiration:
http://www.usatipps.de/tipps/einreise/And you are right, ICAO says all non-machine readable should be out of circulation until 24th of November 2015. Germany already introduced the machine-readable passports, so the system is there. It is the citizen who should ask for a new one. German authorities could have informed all citizens having old passports registered in the databases. However this could be a tremendous effort on local authority side. It is easier that each citizen should take care of this.
To remedy any headache, it is better to request machine-readable passport as early as possible. Because of the date above in the coming months getting the machine-readable passport might take much much longer, since a lot of people will probably ask for a new machine-readable passport which will cause a long queue/wait time. I know my case from Hamburg. I had filed the machine-readable passport request in beginning of April and got the passport End of May (1,5 months later!).