In all honesty, I would definately wait. Its only gonna be another 2-3 months, and you'll have seen the car with plenty of time left to still snatch up an 03 at an even better price if you don't like the new one, or dont feel its different enough to warrant the price difference. From what I've heard there are going to be some welcome improvement like new colors, new wheels, some newer more aggressive styling in the front end, to make the car look less chunky. Maybe some goodies like XM radio. Worth the wait at least to get a look at the car and what its going to offer I'd say. Its just a refresh, but a change nonetheless.
If you want to know what to expect, go somewhere like www.edmunds.com and compare a 1997 LS400 to a 1998 LS400. That was the type of refresh (front end, taillights, wheels, some interior peices, more soundproofing tauter suspension) that we're expecting them to do this time. As you'll see from the pictures. Its not a lot, but enough to make the car look fresher and newer.
Its simply one of the best cars on the road. My dad has a 98 he's put 140,000 miles on and it runs and looks like brand new. He's going to probably trade up to an 04 in October. You wont be sorry.
Welcome to the board!