Audi currently sells a handful of models equipped with a V-10 engine but with fuel economy and emissions standards toughening all around the world we may soon see the end of the ten-cylinder engine in the automaker’s future lineup.

We’ve already seen the V-8 engine in the S5 and new S4 models replaced with a smaller supercharged 3.0-liter V-6 unit, and this same practice of engine downsizing may soon be applied for other models.

BMW is reportedly planning to replace the V-10 engine in its M5 sedan with a new twin-turbocharged unit for the 2011 M5 and according to a new report from Germany’s AutoBild, Audi will do the same for its S6, RS6 and possibly even the R8 V-10 supercar.

Just yesterday we saw a similar report claiming Audi has dropped its V-6 engine from the 2010 model year TT. Other models losing the 3.2-liter V-6 option include the now-defunct A4 3.2 quattro Tiptronic and A5 3.2 quattro manual, as well as the A3 3.2 S tronic quattro.