Managed to install AL V alongside AL 4, and yes, I see only 3,268 presets in V as opposed to 7,311 presets in 4. However, there are a few more instruments available, as well as updated versions of old ones (31 instruments in V as opposed to 22 in 4). You can download the manuals for both versions to see the lists of instruments.
It's good that I'm able to install both (no extra cost to install AL V if you already have AL 4, it seems), but I think it's going to be really annoying to have to switch back and forth to use an instrument that's only available in AL V or a preset that's only available in AL 4. What were they thinking? I wonder if there's some way to copy the extra presets from AL 4 to AL V, so I'd only have to use AL V.
Their naming convention for the different releases kinda sucks too. Could they possibly make it any more confusing?