It's hard enough to fuse hydrogen that we'll probably never do that, little well fusing neon into iron.
The Sun barely fuses hydrogen (the amount of energy produced in the core per sq. metre is quite low, there's just a lot of sq metres) and even when it reaches end of life and much more compact, it'll barely fuse helium. Iron (and nickel) are only produced in the largest stars due to the heat and pressure required.
With luck,we'll get fusing deuterium and such in a controlled energy positive manner.