Can't speak to the Scotia Gold Amex, but Chase is usually very stingy with churning. Wait at least 6 months, I'd say, though some churn-mongers have claimed just a few months after cancelling and reapply with success.

With signs that Chase may be leaving the Canadian scene, they may be getting even more stringent with new applications (eg., they are no longer offering the Chase Amazon.ca Visa card to new applicants, and there's some speculation that the Chase Marriott card may be winding down its days by this July). So on the one hand, Chase may be tough to churn, but on the other hand there may be a closing window on the Chase Marriott card. All speculation though, so wrap it up and give it a boot if you'd like!

There's no need to cancel the TDAVI before reapplying for another one, at least in my experience. Many people have opened multiple concurrent TDAVI cards, and not even waiting the prescribed 6 months (in their T&Cs) before reapplying. But, if you don't want to test those waters then consider doing a product switch to a no-fee TD card, and THEN reapplying...this should safe-guard you from having a cancelled card re-activating on a new application submitted within 3 months after closing it.

I can confirm that the CIBC Aerogold Infinite Visa is still 15K and FYF if you snag a kiosk rep while airside at YYZ (as of earlier this month, May 2017). Allot about 20-30 minutes for this though, so if you have a quick connection to catch, don't bother.