The damage is already done. If things are still working, then you can continue hoping that corrosion does not later form on any electronic components....which if it does will cause the laptop to misbehave or even outright fail. You can wait & hope, risking that it may fail at an inconvenient time, or you can have it inspected & repaired now (or at a convenient time if it continues to function). Most liquids other than plain water will cause a stickiness and binding of the keyboard mechanism. If it bothers you, then yes, the entire keyboard will need to be replaced, but with recent Apple laptops this will require replacement of the entire Top Case Assembly (palmrest & area around keyboard) since the keyboard is integrated into it. More than likely liquid will have made its way beyond the keyboard and may have touched the electronics. If so, then at some point the corrosion which forms will most likely end up causing a failure to other internal components.