This is from AvionicsWest:

"WAAS for the GNS430/530 is now postponed until sometime in 2006. I
don't "think" the problem is really a WAAS issue. You see,
Garmin plans on making the 430/530 comply with TSO 146 just as the
GNS480. TSO 146 requires an update rate of 5hz verses 1hz as the
product now updates at. I've seen the WAAS receiver board while in
Salem, so the hardware is complete as far as WAAS is concerned. Yes,
Garmin has been promising WAAS and TSO 146 for the 430/530 for years
now, they are saying the problem is FAA issues. What would I do about
with this issue if I were the in charge at the Garmin Big House?
Simple, fly to Oregon with 430/530 and had it over the Garmin AT
engineers. Say, "Make it happen" and two months later you would
have a certified 430/530 that meets TSO-146 and WAAS. Those Salem
Oregon engineers are the best in the business."

http://www.avionicswest.com/myviewpoint/aea2005.htm