Unfortunately this is pure speculation and probably not accurate at all. You should be reminded that permanent residency is provided by the government to live in Canada permanently. So in the eyes of the government whether it is 3/5 or 4/6 or whatever else, it does not have an impact on residence as it is assumed that all will be living here. So unless you are planning on leaving the following day you are sworn in, the rule will not change much for you.
Even if you are planning on leaving Canada after you become citizen, a lot of people who became citizens 20 years ago are still being stopped at the airport and questioned about their residence outside the country. The government uses a term for them called "citizen of convenience" you can even google it. I have lots of friends who were naturalized in Canada in the 90s and who live/work in another country who get seriously questioned and sometimes investigated when they come back to the country. While you will not lose your citizenship for doing that but it will leave a mark on you each time you have to do a government application (Trust me I know what I am talking about)
Also logically, any new such rule entails that the government will have to find additional people to handle the large volume of cases, train them, issue new applications, process adjustments, and all this takes time and before all of this is figured out, the government will probably not implement the 3/5 rule even if the bill takes royal ascent. Look at Bill-24, it took the government 1 full year to apply the 4/6 rule while all other articles have been implemented earlier.