i was wandering in the future can bitcoin switch to proof of stake?
No. For any fork trying this an altcoin will evolve. Bitcoin will always be PoW.
No, it could switch to POS, POW is waste to much energy, the more important is POS is more secure than POW.
For big exchanges and even casinos who have alot of funds, they could probably 51% the network without the huge electrical bills.