time for the bitcoin developers to upgrade bitcoin's digital signature and such...
I don't know much about cryptography, but there are few other steps they should do first such as,
1. Choose which one could be used by Bitcoin. Abstract of FIP 203 doesn't mention anything about cryptography signature, so i guess the choice is either FIP 204 or 205.
2. Do through verification about security of each cryptography. Don't forget some older cryptography accepted by NIST may have backdoor,
https://en.wikipedia.org/wiki/Dual_EC_DRBG.
The new address part should be trivial but old clients would have to treat the new form of signatures as instantly valid somehow.
Good thing Bech32m exist, so theoretically bc1z or Bech32m with witness version 2 can be used. As for old client, "anyone can spend" trick could be used again.