Could there be a point where the value of the Bitcoin miners receive is almost zero, and the Bitcoin network collapses due to a lack of miners?
The reward the miners receive is the sum of block reward (that gets halved every ~4 years) and the sum of all transaction fees inside that block. So the only way what they receive could be zero is if we are about a 100 years from now that the block reward is zero and also nobody uses bitcoin anymore to pay any fee.
Is it possible that Bitcoin could increase its total supply in the future? But that would certainly cause Bitcoin’s price to drop significantly.
Anything is possible but remember that capped supply is one of the main principles of Bitcoin. Changing those is extremely difficult because it fundamentally changes Bitcoin.
Not to mention that there is no reason to do so in the near future (that's the next decade or two). And in my opinion speculating about any further than that is wrong because of the way technology advances, we may have something far better than Bitcoin 20 years from now.
Could Bitcoin switch to PoS like Ethereum? That would also cause Bitcoin’s price to fall.
No never because PoS is a fundamentally flawed protocol.