Shadowrun used to be my favorite RPG game, before the Dumpshock people took it over and (IMHO) ruined it.
There is nothing in it that d20 couldn't do. Rule wise, SR is fairly close to D6. Star Wars went from D6 to d20 okay.
A very simple way of doing SR would be to use the Spycraft rules as the core, the cyber rules from OGL Cybernet, and the magic system from Sovereign Stone.
Heck, even if you wanted to keep the same sort of damage system, you could just use the one from M&M, which is very similar to SR.
Anyway, with regards to SR4, reading the press release would scare me if I were still a SR fan:
"# The core mechanics are completely revised to be simpler and more streamlined for quicker, easier and more consistent play.
# Matrix 2.0! An all-new level of wireless “augmented reality” overlays the real world, unleashing hackers to be mobile digital wizards.
# The year is 2070

five years since the System Failure took down the old Matrix, nine years since the passing of the comet unleashed wild and unexplained magic in the world. The Sixth World has changed. Some of the players are familiar, but there are new faces

and new forces

at work in the shadows"
The 3 previous editions weren't very different. 2E and 1E had some big changes in the damage system (as the 1E was basically broken), but 3E mostly added rules to cripple high powered characters. This sounds a lot different. And it seems like they are changing the setting dramatically.