Don't worry, your old URLs will still work, and you can continue to use them. Your old links/URLs will always redirect to your new ones.
We know a lot of deviants are attached to their URLs, so the decision to make this change was not done lightly. Part of the decision-making process involved surveying active deviants, and we discovered the overall sentiment was fairly neutral. Most people did not strongly prefer one or the other — as long as old URLs redirected. But, most importantly, we believe this change will be beneficial for you.
The new URLs will likely increase your traffic: Based on Search Engine Optimization (SEO) experts we’ve consulted with and also other sites that have made the switch, moving away from subdomains is likely to increase overall site traffic from search engines—this means more traffic to your Profiles and deviations.
Subdomains cause many technical challenges, inhibiting site improvement and performance. Browsers treat subdomains like different, individual sites for security reasons and, because of this, more and more website functionality is being limited to working with a single domain. Working around these restrictions makes building new features and maintaining old ones complicated, increasing the time it takes our engineers to complete projects. It also creates “buggy” circumstances while navigating the site. For example, you might have noticed that it sometimes shows the wrong artist’s name in the URL when using the “next” and “previous” buttons while browsing artwork in someone’s galleries — this is a technical limitation that is imposed by browsers for security reasons and was not possible to work around until now.