Gmail officially supports username changes
It's taken long enough.
On Tuesday, Google announced in a short video that it would be rolling out a new feature in the US which allows the changing of Gmail addresses. This is a major move for Google, since they have gone decades now without the feature, leading many to create new Gmail accounts altogether instead. This created confusion and difficulty, especially as Google has centralized their platforms and Google Drive has become much more integral to many peoples' work and lives.

For those with the feature available now in the US, head to Google Account settings > Personal info > Email > Google Account email > Change Google Account email. This feature is somewhat buried in Google's account settings, but the option existing at all is still a plus. Your old email will still work as an alternate address for your Google Account after you change it, and you can only "create one new address every 12 months," says Google.
This brings Google up to Microsoft's level on the feature, who has allowed alternate email addresses like this (like an email change) for a number of years now. However, Yahoo still lags behind and does not allow you to change your account email. Similar to Gmail, though, you can add new mailboxes to your account, effectively changing your username.
Either way, it is still nice to see that Google is allowing for email address changes after all of these years. We will have to wait and see what Google does soon.