As of today, segwit doesn't seem possible in bitcoin, but it does in Litecoin. Maybe Litecoin will replace fiat, and Bitcoin will replace gold.
Gold is precious because of its physical appearance. Unless you're talking about digital gold, I don't see any reason as to why it will be replaced by bitcoin. Gold is used in the technology world. Gold is used as well for luxuries. Bitcoin cannot do those things.
I wonder why Litecoin (or any coin for that matter) hasn't replace bitcoin yet. Even Eth hasn't replaced bitcoin yet. Bitcoin is just too strong right now to get replaced by another coin. BCU didn't even do enough damage to bitcoin. It did a good intro though. But now the coin as well as the Hard fork drama is gone.
Lightning transaction really is a necessity for bitcoin to take over. But we are not at the point yet whereas we need it a lot. Today, the transactions are still almost an instant.
(Plz don't give me the "bitcoin transactions takes too much time to get confirmed" comment because the answer will be "put some transaction fee")