From the article, it looks like future support for other IDEs is definitely possible:
"Visual Studio Code is great. It’s the primary tool GitHub.com engineers use to interface with codespaces. But asking our Vim and Emacs users to commit to a graphical editor is less great. If Codespaces was our future, we had to bring everyone along.
Happily, we could support our shell-based colleagues through a simple update to our prebuilt image which initializes sshd with our GitHub public keys, opens port 22, and forwards the port out of the codespace.
From there, GitHub engineers can run Vim, Emacs, or even ed if they so desire."
"Visual Studio Code is great. It’s the primary tool GitHub.com engineers use to interface with codespaces. But asking our Vim and Emacs users to commit to a graphical editor is less great. If Codespaces was our future, we had to bring everyone along.
Happily, we could support our shell-based colleagues through a simple update to our prebuilt image which initializes sshd with our GitHub public keys, opens port 22, and forwards the port out of the codespace.
From there, GitHub engineers can run Vim, Emacs, or even ed if they so desire."