Keep the 4.0 stuff in 4.0.
The graphics updates in PoP 3.5 are not imported from PoP4. They are perhaps going to be used by PoP4 too, but they were designed/chosen for PoP3.5.
We have about 75MB of new textures in the update so far (and it will increase to about 100MB I think).
On the good side we have converted all sounds to .flac format thanks to Nullpat and therefore we are below the dreadful 2GB RAM limit that will cause Warband to crash. Currently it is at a little over 1.6GB when using 100% texture details and having the "Use textures on demand" setting at false.
The .flac sounds have higher quality than the 3.42 wav files as well. If no sounds are heard, then the player needs to get the .flac codecs though. These can be found here for example:http://www.free-codecs.com/FLAC_download.htm
So, yeah, there is already new graphics and there will be some more before the update is released.