Given the geometric progression of technology, it is impossible to make a claim like this with any certainty.
Only if you have a weak understanding of physics.
Above statement indicates you know absolutely everything to be known about physics and that no technology can ever evolve that will provide a power source that will make extracting Hydrogen from water cost effective.
Have I got that right? If so can you explain why that would be true?
You expect a "hydrogen fuel cell LIKE" power source will use a fake technology like cold fusion? The last I heard they hadn't been able to duplicate it. You might as well wish for a car powered by a mini black hole.
Above statement indicates you know absolutely everything to be known about physics and that no technology can ever evolve that will provide a power source that will make extracting Hydrogen from water cost effective.
Where did I mention cost?
At least you understand it will take another power source to make the Hydrogen. Seems like that would be the power source to use, rather than taking a loss converting into hydrogen.