Huge drop off in Google "indexed" pages after switching to HTTPS, should I switch back to HTTP?

We just switched from HTTP to HTTPS two weeks ago, and after doing extensive research this is what we did:

  1. Added the HTTPS property to our Search console.
  2. Redirected HTTP robots.txt to HTTPS robots.txt.
  3. Placed a new HTTPS sitemap in the robots.txt, and removed the HTTP sitemap URL from robots.txt.
  4. Made sure that the old HTTP sitemap was intact, and made sure it was still existing in our HTTP property in the search console.
  5. Submitted the new HTTPS sitemap in the HTTPS property in the search console.
  6. Made sure the HTTPS sitemap was the only sitemap being updated with new URLs. (Stopped adding new URLs to the HTTP sitemap after the redirects.)
  7. Changed all canonical URLs to HTTPS.
  8. Made sure all 301 redirects were in order and a one to one mapping was intact for all HTTP -> HTTPS.

Currently we will keep the old sitemap for one month from the time of the switch. We can already see a decline in the number of clicks on the HTTP property, and a proportional increase in the number of clicks in the HTTPS property.

Here's what you should see:

Our Search traffic declining on the HTTP property.

Our Search traffic increasing on the HTTPS property.

Are you checking the correct version of the search console? See the Google support site point 4: you need to add the https version as a new site. If you are still looking at the http version it's quite logical that the number of indexed pages is dropping as Google is indexing the https versions instead (which should be visible in the search console of the https version)

This is completely normal. HTTPS is technically a completely separate site, though traditionally, it mirrors the HTTP site. However, search engines cannot count on that. Switching to HTTPS has a cost associated with it. This means that your site has to be completely re-indexed. Part of the reason is that the search index is ordered around URLs as a key. You are, in effect, using a whole new set of URLs.

Your best bet is just to be patient and let it ride.