The gap will remain throughout the generation,as you can't make up better hardware from thin air. Tools will improve,that much is certain, but as developers will be able to extract more from the x1, the same applies to ps4. It's not like Sony will sit on their asses and do nothing to improve the tools. That and the fact that the os footprint will certainly be diminished - as it seems a little bloated for now- releasing more resources for the devs.
Microsoft invented DirectX though.