Not focussing on the actual limits of bitcoins and how one bitcoin has been set limits of many millions of pounds.
What is the potential for the bitcoin price in the future?
What do you mean by the bolded part? Regarding the second line nobody knows the potential, that's up to what potential you see in it. 1 bitcoin could be worth thousands, tens of thosands, a million, or zero or close to it. That's part of the fun.
I have read some websites that suggests that there was a cap on the bitcoin price of around $1000000000 and caps on the dogecoin price at $15000000. Howether, not sure if these are legit and they have changed in the past!