If that happens you're right security budget will be fine. But the argument is there is no guarantee the price will keep going up at that rate. We already see it's slowing down. Consider the subsidy will eventually go away so transactions happening on-chain will be crucial to generate fees for miners.
So 1) price has to continue rising at a fast enough rate to offset decreasing subsidy 2) avg transaction count has to continue increasing on-chain, or 3) a combo of both
Current L2s so far don't help because miners get none of the fees that happen within Lightning, Ark, Spark, and ecash (where most user are expected to transact in the future as adoption increases)
Open to being convinced otherwise, but it seems like a big issue down the road
