Bod:

I'm not a Raspberry Pi guy (yet), but I'd expect it to work like a typical 32-bit x86 installation; meaning that while a single process is limited to 4GB, the OS can have multiple processes running to use the entire 8GB address space of the CPU. So you won't be wasting the capabilities of your 8GB RPi unless you're running just a couple of processes.

...roboticus

When your only tool is a hammer, all problems look like your thumb.