With this modification, it may be possible to make the PC version of SA look as good as the mobile version will look. But the updated models would also need to be converted too.
You can already make the PC version look better.. the mobile version won't look much better than the vanilla San Andreas.
GTA3 and VC Mobile contained some Xbox style things that were never adapted to the PC version, hell, VC contained detail overlays, actual shadows, actual hands, etc, to. San Andreas is the only main GTA in a sense to not get the "Xbox" style upgrade (thanks to Rockstar shutting down Rockstar Vienna and Rockstar North doing a rush port), so now with War Drum continuing that work, we may actually see a San Andreas with a bit of a quality boost.
Well, everything that was enhanced on III and VC was able to be moved over, except the cut scene hands, and detail overlays (which if someone wanted it bad enough, they could move it over). However III and VC on mobile were missing fog and clouds.
As for SA Mobile:
-Enhanced character models, may not be easy to do it exact if its the same situation as VC.
-Enhanced vehicle models should be possible but the new texture and or model formats will need to be cracked if they exist.
-Dynamic Shadows is already being done with SA Render. However, we don't know what they look like yet. They could look like shadows from GTA IV/GTA V, or they could be simple like the PC ones, except everything casts a shadow. We will find this out when it comes. I bet they will be able to be recreated with SA Render on PC.
-Game may have detail overlays like VC, or it may have even better textures to begin with.
-The check point system, well that probably not. I'm not sure if its like GTA IV/V's route lines on the radar, or check points in missions so you don't have to redo the whole thing.
They did say the game was coming to Windows Phone too. I've read some speculation that the game could come to Windows RT and Windows 8 as a Metro app. If this does happen, this will mean the following.
-PC will have the enhancements.
-You would have to re-buy the game.
-You would have to have Windows 8.
-Most, if not all the mods will be compatible with the new version because the structure of a Metro app is different from a regular PC app, and the hot coffee business that prevents many mods on V1.1, V2.0, and V3.0.
-And obviously it would technically be a whole different app from the existing SA PC.