The OpenBSD Project is disinterested collectively (due to Project policy) in any NDA with any vendor for access to proprietary source code under any circumstances. That's the "Open" of OpenBSD.
The Opera port was added at a time when there were very few graphical browsers available for OpenBSD, and it was a useful expedient at the time. I can recall no other binary large object block (blob) in the ports tree.
I haven't seen any follow-on post on ports@ from any individual (or development group) who stated they would open negotiations with Opera Software ASA with the goal of obtaining NDAs and other appropriate contracts with Opera, with the intent of porting their newer browser to OpenBSD or other BSD-based systems. If you wan't to investigate what it would take, you're welcome to contact Opera and ask.