Im far from being a programmer or even understanding it, but my I read that it is just a matter of adjusting the shaders textures.
No, it's not.
If it was so easy, you would see way more airports compatible with DX10, while our recent ones (KDFW, KLAX, CYVR, plus JFK) are amongst the few. For airports that were made using FS8 code, which means LSZH, LSGG, KORD, KLAS and all Hawaii airports, it basically means reworking most of the ground polygons.
This means we'll have to undertake this one step of a time, while doing the airport remakes that we'll do it over the years, to keep them current with the airport current status.
Right now, we are updating JFK that, incidentally, didn't need a DX10 update to begin with, but had to be updated anyway, I guess the next likely candidate for an upgrade might be KLAS, so we'll surely take time to make it DX10 compatible too.
We are strong advocates of DX10, but these things takes time, eventually everything will be DX10 (and DX11, for P3D 2.0) compatible.