Yes, your skill AVs raise, because your skills are based on those Attribute numbers. Your Guns skill, for example, may be listed as "+5", but that's +5 from the base Dexterity score. If your dexterity improves, it makes sense that your Guns use would naturally improve.

I thought this was explained somewhere in the rules, but I can never find it when I want to reference it. Seems to me that it's one of those rules that's tucked away inconveniently somewhere. But I may be making the whole thing up. I swear I looked it up before, but if not, it only makes sense to play that way, I think.

I mean, how could one explain that their Magic score went up, but they weren't any better at casting spells? So that's the way I do it, even if it's not official.

It is explained at the beginning of the skill-section in the main book, in the "getting tougher"-section and at the beginning of character creation: skills are based their secondary attributes and the AV is formed through the addition of the skill bonus and the secondary attribute.

Only exception is at character creation, if there is an "=15" oder a "[max 12]" designation. In this case, the skill bonus is reduced to the corresponding number.

SYL