Pat,
I definitely think GCA has some influence in this. With our fortune of having some of the best golf architects in the world on this website, it would seem inevitable that the discussions here would have a least some impact on the amount of restorations in recent years.
That being said, I think another big reason for restorations is because less and less golf courses are being built. This could be attributed to a lack of land for which to build (which probably isn't the case as I know there's a bunch out there, just not as much as in previous years, especially with environmental regulations getting stricter), or probably more so to the fact that the number of golfers in the country doesn't seem to be increasing, hence why build a lot more golf courses when the market isn't getting any bigger. That being said, with less golf courses being built every year, this perhaps has changed the focus from building as many new courses as possible to making the courses we already have that much better. Thus, the increase in renovations.
Ultimately, I think there are several factors relating to this trend, with GCA indeed being one of them.
I think it would be difficult, however, to find legitimate evidence linking the many recent restorations directly to GCA. How could you measure that effect?
The question above would actually be fun to explore, as though we are a very small part of the overall golfing community, we are at the same time are a very well respected group of that community.