I read Exceptional Attribute as raising the natural maximum for an attribute by one.
Sorry I was on mobile phone when answering this specific claim yesterday. As many things in this book it is ambiguous and you can find arguments to read it both ways. Here are some arguments that support the idea that your natural maximum attribute does not change when you take exceptional attribute.
p.72 Exceptional Attribute
Exceptional Attribute
Cost: 14 Karma
The Exceptional Atribute quality is how you get to be the charismatic troll, or the agile dwarf. It allows you to possess one attribute at a level one point above the metatype maximum limit. For example, an ork character with the Exceptional Attribute quality for Strength could take his Strength attribute up to 10 before augmentations are applied, instead of the normal limit of 9. Exceptional Attribute also applies toward Special Attributes such as Magic and Resonance. Edge cannot affected by the Exceptional Attribute (Edge is raised by another quality called Lucky). A character may only take Exceptional Attribute once, and only with the gamemaster’s approval.
p.65 Metatype & Special Attributes
Several metatypes also receive physical or mental advantages/disadvantages to their attribute ratings (such as higher or lower natural attribute limits).
p.66 Metatype & Special Attributes
Note that for most metatypes, the maximum rating for Magic, Resonance, and Edge is 6; humans have a maximum Edge rating of 7. Certain qualities (Lucky, Exceptional Attribute) allow characters to exceed attribute maximums by one
p.67 Example Rob that possess Exceptional Strength Attribute
He got a listed Racial Base / Natrual Limit of 5/10(11)
- Indicating that his natural limit is 10, but due to the quality have an exceptional limit of 11 (which let him exceed his natural attribute limit by 1).
p.66 Mental and Physical Attributes
State that you can only have one attribute at your natural maximum limit at chargen; It might or might not mean that you can not have a have a human with agility 6/6(7) and strength 6/6 at chargen even if you have exceptional attribute agility; but it would let you take agility 7/6(7) and strength 5/6.
p.456 Customization of cyberlimbs
State that you can only customize cyberlimbs to fit your frame and body [which might or might not mean your natural rating - not the point I am trying to do right now] but it also state that you can not customize cyberlimbs beyond your natural maximum for that attribute - witch might or might not indicate that you can never customize the limb above metatype racial maximum... even if you have a natural rating that exceed the natural maximum by one point because of exceptional attribute.
But, as I said in the beginning of the post; There are also arguments that exceptional attribute increase your natural maximum.
p287 talks about only ceasing to be an awakened character if your max reaches zero.
On the subject about losing your magic powers forever and ever the text on p.278 (not p.287) does not even talk about natural maximum nor your metatype maximum attribute rating in the first place. This rule only mention your maximum magic rating. So in this case the question if Exceptional Attribute increase your natural maximum rating or if it let you exceed your natural maximum rating might not even be important at all.
Maximum magic rating might or might not read as the total of your metatype maximum attribute rating plus exceptional magic attribute plus grades of initiation minus loss due to essence [Cyberware Essence cost or the Essence Drain critter power].