Correct. The base unit in Lightning is already a millisatoshi (msat), or 0.001 of a satoshi. So even if one satoshi = $1 (which as pointed out above, would result in the marketcap of bitcoin being around 25 times higher than the amount of broad money in the entire world), you would still be able to divide down to the equivalent of 0.1 of a cent (which is obviously more divisible than fiat). And this is without even mentioning that fees on Lightning are generally a fraction of what they on chain.