As long as the block size remains unexpanded and no significant improvements are made, the Bitcoin network could become congested and transaction fees could spike at any time.

According to some reports, transaction fees have improved significantly as transactions on Bitcoin's mempool are at record lows, with the mempool even being empty at times. This shows that on-chain transaction demand is decreasing significantly, not that bitcoin transaction fees are improving because the network is improving. So we cannot expect this to be sustainable or last forever. Because at some point, the demand for on-chain transactions increases, the network becomes congested and high fees are inevitable.