I also used to think that they might hold the date unknown until the very last moment, but I've changed my mind after the reminder and the 1 month comment period published in the Gazette back in Mid-March.
There will be enough notice in advance.
The changes are really big and complex and I don't think they will be ready before July.
All these changes involve New IT implementations, Training, Waiting for the new legal authority which will give CIC the chance to share personal info, Establishing new Info channels between CBSA, CRA, CIC... The list is goes on and on...
On top of that there are parts of that Bill which are expected to come in force before the major portion, For example The new authority to revoke the Canadian citizenship.
They are not ready yet.
The changes are more complex because of the fact that not only CIC as institution is involved.
That's the reason why there is still no official date, Month and season.
These huge changes needs time.