We are near a 5-year high, mostly due to a meteoric rise this year up untill today.  I would find it very difficult to justify being out of the market for thirty days at this particular stage.  

I don't expect any serious down pressure on the SP this month because lot of tax loss selling doesn't wait this late into the year and because of the current SP momentum few will want to step out to the sidelines for thirty days.

FWIW, and as I have suggested to another member here privately....one strategy worth considering in this situation is to first come up with enough cash (on hand, or short-term borrow) to make your TFSA contribution and with this cash buy shares before they go higher.  Then after waiting thirty days you can sell off the same number of shares (or dollars worth) from your taxable/open account to retrieve your cash and return to your original shareholdings level, but with a tax loss triggered.   Of course because of the thirty day wait this strategy is too late now if you need a tax loss in 2020.