It can't be entirely lost. The possibility will always be there. That 51% of the network's hashing power is controlled by a single mining entity or group is a possibility that doesn't completely go away.

But the odds or probability of it happening may change. The cost of attacking the network grows over time. Mining isn't cheap. Getting more than half of the network's hash rate is extremely costly. The mining environment is highly competitive. As a matter of fact, just a couple of days ago, the network's difficulty has once again registered another ATH.

Further, vis-à-vis the high cost of the attack is a poor return. It simply isn't cost-beneficial. If it's used supporting the network though, there is a nice profit.