There aren’t any negative consequences, as far as I know. You don’t need to extend your PR, you will continue to be a Permanent Resident. You will not be able to renew your PR card till you meet the residence requirements. You’re not rendered ineligible when it comes to apply for citizenship, it’s just that you need to wait till you’ve established the residence requirement.
Residence requirements look at a rolling time window, so lets say that you move in Q3 next year and you’re let in without issue. Then come 1.5 years down the line, your PR card will expire but not your PR. None of your benefits or work authorization expire. So in a further 6 months time, you are able to apply to renew your PR card as you have now met the residence requirement which is that you need to be physically present for at-least 2 years in the last 5 years. And a year subsequent from that, you can apply for citizenship.
Though I must note that come Q3, at the point of entry you may be quizzed and if the border officials aren’t convinced of your intention to stay as a permanent resident, they may open up formal proceedings where you will then need to go before an immigration judge. (I’m no expert in these matters but if your term of permanent residence is valid and you are able to establish that you’ve become a legitimate resident, then the judge would most likely look favorably on your situation. Don’t take my words at face value, talk to a real immigration attorney about this; not an immigration agency but a real lawyer)
So if your question boils down to what is the optimal time to renounce Permanent Residency, then I think the answer should be as late as possible. There are no points for renouncing it early, nor is there any penalty for renouncing it late.