I think it's a pedantic point, as I believe that language is as language does.... however, there's no reason why it couldn't be like "gold", which is also highly divisible. You need the "s" plural for things that can't be divided (like dollar bills). Thus, we don't get paid in "golds".
That said, semantically, coins aren't usually thought of as divisible things in a modern context-- they are pluralized, so bitcoin will probably be pluralized in the same way.
That's my thinking. Bitcoin is an outlier because "coin" is usually indivisible, where as "bitcoin" certainly is. You're never likely to see a price of more than one anyway, making the plural almost completely redundant.
That said, semantically, coins aren't usually thought of as divisible things in a modern context-- they are pluralized, so bitcoin will probably be pluralized in the same way.