GPT-3 and these kind of natural language generators in general can already present opinions if prompted to do so. Depending on what you mean by "opinion", you might also require some memory to let it be consistent in what opinions it presents to you. (Not that humans are always consistent either.)

If you dig any further than this into the question, you quickly get back to the age-old question of "when is it 'real' consciousness and not just an automaton that acts and sounds conscious?"