2. Bitcoin L1 gets mass adopted either through using the UTXOs themselves or by using some project on L1 like Ordinals, Runes. Fees skyrocket to 100+ sats/vbyte, and regular people use Lightning instead. (This would copy Ethereum's outcome.) There is no hashrate exodus, or attack. Prices probably don't cap until 2140 or even later.
3. Block size limit (on Bitcoin L1) got increased. Fee rate doesn't skyrate so much, where people split between using L1 or something else (LN, sidechain, L2, etc.).