Just had a look what bicubic-upsample is and I think it might actually look nice but I'm not sure. What do you think?
bicubic-upsample: http://www.cse.cuhk.edu.hk/~leojia/projects/upsampling/index.html
detail texture method: http://wiki.splashdamage.com/index.php/Detail_Textures
Softer textures with some grain?
To be frankly I don't think Bethesda/id Software is going to invest in re-texturing Rage similar to what EA/Crytek has done with the Crysis 2 hi-res pack but you never know... if Rage sells well? ... maybe?