News Courtesy of Yoast.com:
Site migrations are probably not on most people’s fun list. Alas, sometimes they’re necessary to ensure the continued health of a website. Once you’ve decided you need to do a migration, it’s important to make sure you know what you’re doing and make a plan for how to approach things beforehand. Whether you’re moving from HTTP to HTTPS, switching your TLD, or moving to another domain: think about what you need to change, and make sure you can easily pinpoint the cause if something goes wrong.
The impact of a site migration
“Well, yes, you’ll lose rankings, because you have to migrate it, so you’ll have to take a bit of a hit. It’s probably a better idea in the long run, though, so I would still do it. But you have to realize that for somewhere between three and six months you will take a loss in traffic. That loss in traffic can vary: I’ve seen less than 10%, but I’ve also seen more than 40%. So, it can be quite a painful experience.
But it’s worth it in the long run, especially if that other domain is not used anymore, because otherwise, that reflects poorly on your business as well. So I would take the hit, and do it. Good luck.”
Ryan’s Take 
When I first read the title of this article I assumed Yoast was talking about hosting migration. Such as when you move from shared hosting to a VPS. Or switch providers like going from Godaddy to Dreamhost. Several years ago I had to migrate dozens of websites from one hosting server to another. That was an agonizing experience, but it was seamless on the front end. There was no effect on rankings because only the IP address changed (and some performance gains from upgrading).
It was after reading the first few sentences I realized Yoast was referring to moving to a different domain. Migration is a word I would not have used to describe this. None-the-less, if you’re following the best SEO practices, your rankings really shouldn’t be impacted that much. Maybe your business name has changed. If so, it still makes sense to keep that domain for a couple years and phase it out rather than let it expire.
Using 301 redirects, you can easily send visitors from the old domain/page to your new domain and appropriate pages. MOZ estimates that some 90 to 99% of link power is transferred from these redirects. The whole process should be a gradual transition. A simple banner message for a few months explaining the transition will help eliminate confusion to visitors.
I’m not sure where Yoast is getting their traffic data from with the reported 10%-40% losses. That sounds like bad on-site SEO management to me. In fact, Google Search Console (old version) has a change of address feature that was created for the purpose of transitioning. They don’t want you submitting duplicate content and cluttering their results pages.
I agree that you should make the switch if it suits your business and not be wary of the consequences. Yes, there is a slight chance of a loss in traffic. However, if done right, that loss should be minimal to non-existent.
