Will a Pokemon ever reach its 'Base Stats' potential??

Please excuse me as I know what I want to say, though this may come out a bit jumbled;~

So my [Insert Pokemon Here] has a base Attack stat of 263 and an Attack IV of 15.

From what I can see, the calculation for working out the Pokemon's Attack is (Base Atk + Atk IV) X Multiplier.

From what I can see, the multiplier for Level 40 Pokemon is 0.79030001.

So if I wanted to work out the 'true' Attack power of said Pokemon my calculation would be (263+15)x0.79030001, which = 219.70.

So with my Pokemon at Level 40, with an Attack IV of 15, does it never reach it's full 'potential' Attack power, or is there an assumption/calculation/step which I have missed? I'm certainly no Maths professor, and I don't pretend to know all of the ins and outs of Pokemon go, but I would like to understand the process a little better and potentially use it to prioritise Pokemon a over Pokemon B etc.

Many Thanks for any replies