While I have avoided, and for the most part will continue to do so, the guessing game as to when certain provisions in Bill C-6 (like the 3/5 rule, which is the one of most interest here) will come into force, I would caution against planning based on an expectation of when the 3/5 rule will apply. There are, for example, many reasons why the 3/5 provisions might not come into force anytime soon. The logistics of implementing any change like this are daunting (it took the Conservatives nearly a full year, despite how important it was to Harper and company to get the longer and more strict qualifications implemented), and most of what needs to be done to implement the changes cannot be done until after the Bill becomes law (spending government money and resources without a legal basis is generally frowned upon -- although, allocation of resources could be explicitly included in the budget, which when adopted becomes law, so as to begin the work sooner, but this is not likely).
But also, as many have been referencing, there is likely to be a flood of new applications almost immediately after the 3/5 rule takes effect, and the government is almost certain to more or less carefully choreograph the transition to be prepared, as much as practically feasible, for this.
In contrast, the Bill itself is more or less likely to proceed through the process fairly quickly, subject to potential stalling by the Senate, given that (1) adopting Bill C-6 into law will demonstrate the government is fulfilling its election campaign promises, even if parts do not actually come into force until much later; and (2) there appears to be some urgency in getting the repeal of Subsection 10.(2) in the Citizenship Act done, which is one of the provisions in Bill C-6 which will take force as soon as there is Royal Assent (thus effecting the a Canadian is a Canadian is a Canadian policy).
In sum: I would caution against expecting the 3/5 rule to take effect any time soon no matter how quickly Bill C-6 is adopted.