EA has updated their official Ultima Online: Stygian Abyss website with a dozen commonly asked questions about the expansion pack. One example:
Will the SA client be taking advantage of the higher resolution art, or will that cause too much latency?
This is something both the engineering and art teams spent a great deal of time investigating. There are many reasons why we decided not to increase the resolution of the art.
For one, there are over 16000 pieces of environment art in the game. Recreating all this art in a higher resolution is well beyond the scope of this project. The legacy environment art looks great and everyone is familiar with it, so we decided to stick with it.
Animations are a different story. We certainly have the capability of rendering our animations in a higher resolution. Unfortunately, due to the fact that our animations are 2d, most machines can not handle the increase in data traffic being sent to the graphics card. You may recall players claiming that the Kingdom Reborn made graphics cards "smoke". We are hoping that by reducing the animation sizes by almost 30%, we will alleviate this problem on most systems.
We are dedicated to providing the players with the highest quality art possible, but at the same time, performance is our number one priority. The last thing you want is for the game to freeze up on you while you are being chased by an Ogre Lord. :)