IMO you are damned if you do and damned if you don't. If you announce targeted delivery time, it will be taken like Gods word to his people and delays will make supporters angry. If there are difficulties and you need to postpone even further you will make supporters even angrier and after that the negativity will be having it's own life that cannot be controlled with any amount of communication. Openness is not one way road, it requires something from the audience also (ie. understanding and good will), otherwise it will only result negativity. This is why I don't believe in openness-ideology anymore. And that's why Sailifish-venture will be my last take on anything community related.