If there was a universal community consensus to have a tail emission (Peter Todd's proposal), then it would happen

But there are multiple flaws in the "security" and "51% attack" claims

Bitcoin mining is not "security" in the sense that the hash rate must be never be allowed to fall. The reward falls. Fees are always small, because the fee is set by the sender, not the miner. The hash rate will fall, and will fall far enough that there will one day be more idle hashes available to an attacker than the hashes in the mining network

But a 51% attack has no reward. And if a 51% attack happens, Bitcoin keeps on working

A tail emission is a small amount, not high enough to prevent the rise of idle hashing power sufficient to 51% attack. A tail emission might move the timing of this hashpower "flippening" a few months forward, not prevent it