The next immediate update, which will be released very soon, will allow for 3 cargo loaders to work at the same time, in order to use the Main Cargo door of freighter airplanes everywhere.
We are also working on more complete integration with SODE and jetways. All the work that has been made to support the KSDF Cargo Stands, will have an effect on how jetways will operate everywhere, even if it might not seem that cargo stands and jetways are related.
But yes, surely the 64 bit platform would allow things which were impractical before, like visible passengers.
Note that, although we announced we would stop making new products for FSX, it doesn't mean we are dropping out of FSX entirely with existing products so, it will be a while before GSX will be a P3D4-only product.
It will be more likely we'll have P3D-only *features* added on top of it, like better Docking Systems, Visible Passengers, better animations (P3D allows for more realistic human animations), but the core program will still continue to work in FSX too.