I will predict 2 buffs.
1. DS gets increased movement speed and possibly movement duration. Possible CDR.(Unlikely)
2. Courage grants more MR/AR, CDR, and if they are really nice granting 40% damage reduction at lvl 5. I can see granting the extra resistance and lowering the cooldown being realistic. Frankly, unless you have over 30% CDR and have courage maxed out, its really terrible. U will likely only use it once per teamfight and might even use it at the wrong time and waste it entirely. Hopefully they will lower CD drastically and bring him up to par with other champs who can spam shields constantly. I would even take a damage reduction nerf like only 25% if the CD were lowered by about 25%.
What do you think? Ive been enjoying Garen recently and cant wait to see what they are doing with him.