When buying the 11th Edition rule book, should I also buy the code for my army from 10th?

Hi, I'm new to the hobby and I'm staring with the Adeptus Custodes for my first army, and I wanted to ask if I should buy their 10th edition codex or if I should wait for their 11th edition codex, or if their rules come with their rules come alongside the 11th edition rule book? I just wanted to know, thanks in advance!