Just to compare how the last citizenship changes came into force, and what was the timeline CIC adopted it.
June 19 2014: Bill C-24 Received Royal Assent
http://www.parl.ca/DocumentViewer/en/41-2/bill/C-24/royal-assent/page-24
June 4, 2015 Canada Gazette: Order Fixing June 11, 2015 as the Day on which Certain Provisions of the Act Come into Force
http://gazette.gc.ca/rp-pr/p2/2015/2015-06-17/html/si-tr46-eng.php
Note that announcement is only 1 week prior to changes coming into force.
---------------------------------------------------------------------------------------------------------------------------------------------
June 19, 2017: Bill C-6 Received Royal Assent (exactly 3 years after C-24 received royal assent)
3/5 rule expected to be implemented during fall of 2017
Watch for the dates on which Canada Gazette Part II publishes for the announcement of effective date.
I think it will be about a weeks or maximum 2 weeks' notice!