Yes, there is a top!
There are practically just over 15 million BTC that can be purchased on the face of the earth, there are 118 trillion dollars issued by the American government, the greater the adoption as a reserve and the greater the acceptance as a currency, the greater the value.
I did not include the other currencies in this calculation, an absurd and surreal calculation to make is 10% of the world's capital converted into BTC.