One of the unquestioned assumptions we often run into in discussions of the canon is that it took Christians a certain amount of time to elevate the NT to the canonical status of the OT. But it isn’t obvious what that assumption is based on.
1. Presumably, that assumption hinges on something like this: Jews had venerated the OT for centuries, so there’d an initial barrier to overcome in raising the newly-minted writings of the NT to the same exalted status. That’s not something which would happen overnight.
Now perhaps there’s some truth to this argument. Indeed, many Jews never made that transition. They never became Christians.
2. However, even on its own terms, it doesn’t follow. After all, an OT prophet like Moses or Isaiah didn’t ask his audience to mull over what he said for a few centuries before honoring his message as the word of God. No. The obligation to believe and obey was instantaneous.
There was, of course, a distinction between true and false prophets, but if a prophet was a true prophet, then his message demanded immediate acceptance.
3. But even if, for the sake of argument, we postulate that Messianic Jews were somewhat reluctant to acknowledge the NT writings as Scripture, most converts to the Christian faith were converts from paganism, not Judaism. And I don’t see that a pagan convert to Christianity would have any psychological threshold to cross before receiving the NT writings as inspired Scripture. Nothing over and above his conversion itself. For the OT was never his standard of comparison.
If anything, his heathen background might predispose him to be too inclusive rather than too exclusive concerning what was “inspired.” Too indiscriminate rather than too discriminating.
4. We do have an intermediate group: gentiles who converted to Christianity via Judaism. In other words, gentiles (Godfearers, proselytes) who first converted to Judaism, then converted to Christianity.
But in their case, I don’t see that accepting the NT as Scripture would be any more of a hurdle than accepting the OT as Scripture. After all, they already came to the OT from scratch.