This does not really create tail emission though, it creates temporary tail emission where part of the mining rewards have to be delayed so that they are received at a later block far past the year 2140. It is no longer possible to do once the block reward is completely exhausted.
There are many solutions to that:
1. Forced Soft Forks:
https://petertodd.org/2016/forced-soft-forksSo what is a valid Bitcoin 2.0 block? It could be anything at all! For example, the inflation schedule can be changed to make the coin supply unlimited.
2. Changing coin ownership, without touching 21 million coin limit: from the economical point of view, it is equivalent:
Imagine there are 21 million coins, distributed to many different users, and the block reward is zero. Then, imagine that 21 million coins are produced, because of tail emission. Then, you can have two systems:
1) with fixed supply, where everyone will lose half coins in explicit way, and they will be taken by miners, because of tail emission: 10.5 million coins will remain in users' hands, 10.5 million coins will be taken by miners, 21 million coin limit is untouched
2) with infinite supply, users will have exactly the same amounts, but they will be worth 50% less than before, because miners will be always rewarded by new coins, because of tail emission
3. Introducing zero satoshis, and treating them as non-zero amounts:
So, you know what is needed: zero satoshis. Then, it is possible to create some additional outputs, send zero satoshis there, and use "<anyStandardScript> <newAmount> OP_DROP" as an output script (or this "<newAmount> OP_DROP" could also be placed inside witness script, or as an input, many things are possible). It could be handled in the same way as Segwit vs NonSegwit: if it was possible to create a situation, where old nodes cannot see new signatures, then it is also possible to create a situation, where old nodes will not see new amounts (there could be many reasons, for example if hiding amounts will ever be introduced, then it is reasonable to put zero for backward compatibility, but the same solution can be used to introduce any coins to the system, because the size of the UTXO set is not limited). And then, it is all about human factor: if those zero satoshis will be really used to move real values, then they could be traded, bought, sold, and used in real life. If it is possible to create NFTs out of thin air and sell them for millions, then why producing coins out of thin air and selling them for real goods and services wouldn't work as well?
4. Something else. There were many ideas, just read the whole topic about tail emission:
https://bitcointalk.org/index.php?topic=5405755.0They cannot verify the post-softfork transactions.
If you make it explicit, by taking single satoshis from users, instead of producing new coins, you will reach identical economy, while preserving backward compatibility.