CBDCs will not replace fully the paper money. They just can't. And not all governments will issue CBDCs.
It will take more generations until paper money gets phased out, if ever. There are still many people who don't use technology, there are still many regions not covered with internet; those just cannot go without an offline currency.
That's what I've thought. But if governments are keen into pushing digital payments, then they're going to have to provide the necessary tools to make it happen. I believe the transition from physical to digital Fiat will be a slow one as not everyone is used to credit/debit cards or even in-app purchases. As you've said before, there are many people without access to the Internet. Not only that, but there are old people who don't like to use anything else other than paper money to pay for goods and services. Governments who issue CBDCs are going to have to experiment with it for a while before the transition is 100% complete.
Of course they're pushing it. Paper money needs printing almost continuously. There are always banknotes that get damaged and they'll get burned (or melted) and replaced with new ones. That costs money.
If they manage to reduce the amount of "paper" money needed to stay in circulation to half, they will save a lot of money from this cycle.
Then, obviously, digital money - no matte it's banks, visa or CBDCs - it's easy to track.
And, as we already know, CBDCs will probably also be easy to freeze or seize, giving governments even more power.
But, by the law (or possibly the constitution?), the government has to ensure each and every citizen has access to the money. And if internet and technology is not available.. phasing out paper money will be illegal/unconstitutional. Simple.