As far a DX11 support goes we should also keep in mind that PS4 will be launched later this year and it supports DX11 and from what i have read its architecture is similar to pc, so by supporting DX11 for pc they can also port it to PS4.

I think PS3 memory is the reason for low res textures and low end pcs as well and since this game is in development for less then 2 years which is very short period of time as far as mmo are concerned and high res textures will only benefit high end pcs they decided to implement it after the launch and maybe we get more then just high res textures and few DX11 features because of PS4, that is if there is a PS4 version.