Some interesting info folks.
Max level is 70 which means 69 skill points earned through leveling, this does not include additional skill points gained through Places of Power.
Combat (Red) skill tree has 20 skills total with 2nd, 3rd, and 4th tier of skills opening at 10, 20, and 30 skill points invested. A total of 91 skill points is required to max out the entire Combat Tree, which is naturally is impossible unless you invest all 69 levels worth of points and find an an additional 21 Places of Power.
Signs (Blue) skill tree has 20 skills total with 2nd, 3rd, and 4th tier of skills opening at 6, 18, and 28 skill points invested, A total of 79 skill points are needed to completely max out the Signs skill tree.
Alchemy (Green) skill tree also is 20 skills, 2nd tier needs 8 points, 3rd tier is 20, and 4th tier is 28. A total of 90 skill points to max the entire tree.
Yellow skill tree has 10 skills for 10 points each.
There is 70 skills spread across the 4 trees at a grand total of 270 skill points needed to max out everything.
In short it is not possible to max out every single skill in the game. You have however with some careful planning and enough Places of Power visited acquire enough skill points and getting to level 70, it's possible to at least have enough points to max out 15 to 20 skills total of your choosing.
Since you can equip a max of 12 skills total upon reach 30. There should be a enough points to obtain to max out any 12 skills of your choice.
On top of using Potions of Clearance you have good degree of flexibility to tailor your Geralt.
But know that you won't ever come to making some ultimate maxed out Geralt without a mod that gives more skill points per level.
Plan your builds carefully folks, and have fun!