in future im sure bitcoin will be stable at ~$500 (after mining ended)
more country will be use bitcoin, and bitcoin will be number 1 online payment
If the price of Bitcoin is just $500 per coin after practically all have been mined, then it means Bitcoin never caught on to mass adoption and is ultimately only used for speculation. $500 per coin puts Bitcoin's value at just 10.5 billion, and with consistent inflation I imagine that number is actually of lesser value than today's market value.
On the event of halving people are expecting bitcoin prices just would double. From past records and analysis halving will trigger bigger buying pressure to flow in new money into bitcoin eco system causing bitcoin prices to claim at least 10 times of current prices.