Google advises to combine the use of HTTPS and change the URL structure
The transition to HTTPS and change the URL structure is best done at different times. This Council gave a Google spokesperson John Mueller during a regular hangout for webmasters.
Question of the webmaster was that the company plan to move to HTTPS and in parallel with the numeric URL to the URL with keywords. However, they are not sure that this should be done at the same time.
Mueller said that the combination of these tasks is not the best option. When Google sees a change to the Protocol or domain name, it is easier to handle these changes, provided that the URL structure remains the same. Otherwise, this process will last longer.
Listen to the question to Mueller and his answer is, starting at 40:20 of the video below: