But holding till September 2025 would be worth it since the bull run will last till then.
It depends on your plan. For me, as long as you will sell at the peak or near to it then it's all worth it. It's worth the wait when you sell your coins that you're holding at a profit.
My question is who buys Bitcoin at that price..?
Those who want to buy it.
Many also question that in the past. Who will buy Bitcoin at $30,000? At $40,000? At $50,000 and so on. There will, and will always be buyers at any price because they believe that they can still get profit even though the price is too high already. I guess this is also there reason why there is a thing called "Greater Fool Theory".
Will the value of Bitcoin keep increasing after then?
As long buyers are way more than sellers then the price will continue to increase.