My thoughts on this -
We don't have any hard information yet, or even good speculation. But my guess would be that there won't be any major enhancements to the '05. There may be a minor tweak or two, and probably one new color. And it will probably cost you a bit more. If you like the color of the '03, and think you are getting a fair deal on it - buy it.
The Yamaha Majesty has a good reputation in other countries were it is sold. But until it is actually here, and in showrooms, and priced for the US market, it is not a contender. If Yamaha is delayed on their release of the model, or if the dealers near you don't even get one initially, that is time lost that you could have been enjoying the Burgman 400. And again, a new Majesty promises to cost you move than a leftover AN400.
If it were me, I'd be negotiating on the purchase of the AN400.