I wonder if the fact that there were so many pottery shards (250,000) found at the site could be interpreted as evidence of St. John (or, at the least, others at the time of the saint) would baptize a person without immersing him, i.e., that baptism by pouring would have been common?
If that were true, that would seem to cast doubt upon the interpretation of various New Testament passages by some Protestants who claim that baptism in the time of Christ and John was always done through immersion and therefore conclude that if we want to be a New Testament Church then we are obligated to regard immersion as the only valid form of baptism.
But I suspect that even if such an argument was plausible given what we know about the cave in question, we shouldn't hang our collective hats too much on it. If we did, we certainly wouldn't have learned the lesson of the supposed ossuary of James and all of the folks who were so quick to make so many conclusions based on its supposed discovery.