However, as Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC), I believe this "6-confimation" acceptance policy will change to include not only the number of confirmations, but the timing of those confirmations as well. Consider a scenario where an exchange deciding whether a tx with 6-confirmations that took 4 hours to arrive (this happens occasionally) is safe to consider finalized/settled. Even though 6-confimations may be considered safe by today's acceptance policies, this tx would still have a high probability of double spend due to the assumed 4-hour long wait for the 6 confirmations (as the attacker would have 4 hours to produce 7 blocks instead of the normal/expected 1 hour). Instead of ignoring block interarrival timing, it may make sense to include block timing as part of an acceptance policy.
So, going forward Bitcoin acceptance policies may change from today's 6-confirmation standard to something more complicated that involves the amount of time those blocks took to arrive. This would significantly enhance Bitcoin's double spending resistance without adding/altering any code and may give the network a much needed security boost in the coming years to prevent the attack discussed in the post.