segwit should be deprecated and wallets should encourage users to move their UTXOs to taproot quantum resistance is a far future risk. the best option we have currently for switching to quantum resistant signatures and ECDH is an algorithm called VDOO which has 96 byte signatures. so such an upgrade is not really feasible before 5 years when there might also be low enough storage prices to justify such a switch. the danger of bitcoin addresses being cracked is completely unrealistic in the short term (less than 10 years). the smallest economic UTXO to attack right now is over 800btc and it would take about 2 weeks to do it, assuming someone builds a big enough machine to do it, which is gonna cost upwards of 50 million dollars in the first place, plus that much again to power it for such an attack. also, segwit witness discount does not make transactions as much cheaper as taproot. taproot can combine multiple signatures allowing many UTXOs to be merged with only one signature block.