Maybe i'll postpone buying the game to october 2016, to better prepare myself for the extra content...

This actually because of them implementing high fidelity sub-millimeter fully dynamic, tessellated head stubble that's even factored into the subsurface scattering calculations. Compute heavy! Tesla recommended

On top of that, we're going for a new release model where we put out a good chunk of the game when it begins and then release the remaining locations over time.

What they really mean is so they can break the game up into more DLC missions it sounds like.

Looking that it is the same for DeusEX, and this fall at the same period of the release of Tombraider. I can imagine, instead of implement DX12 by a patch later ( as it was initially rumored ), they have decided to get all the pc version launch directly with it. ( as confirmed by AMD about DeusEX ).