No, it isn’t. Opening CUPS to the whole internet is just plain dangerous. If I want to print at home over CUPS, I could set up a VPN and then print there. But this is not practical, hence the question about a feature that resembles Google Cloud Print (sans the privacy/confidentiality problems).
The idea would be to have a plugin/app that lets you access your printers from anywhere over the internet and Nextcloud acting as a gateway. The printer could be connected to the Nextcloud box or another computer with a printer attached/set up with a connector waiting for jobs sent to Nextcloud by the clients. Also printing documents directly from the Nextcloud web interface would be great.