As you are probably already aware, Apple has updated their new iPhone releases so that all the new iPhone12's have 5G capability, whether you wanted it or not. Does it matter? Not really, according to this article. When/if 5G is available in your area, the iPhone 12 will handle it just fine, but it will also work well with the existing 4G network, which probably is what most of us have now.
If your only reason for a phone upgrade is just to get 5G capability, it probably isn't worth it, according to the article. But the iPhone 12 has other new features which may make this an attractive purchase right now, 5G notwithstanding.
Jim Hamm