Make sure you max out your companion’s affection and finish their stories. You will not be able to go back if you start the knights of the fallen empire. If you max out your affection with your companion’s the better they will be when it comes to fighting.
Also I would suggest to max out your crew skills so you will be ready when the expansion is released. It would be one less thing to do when it hits and you will be ready to start crafting the new stuff.