I've thought about this myself, and I've had to 
ask myself, "why are the cost of cels going 
down?"  Is it because the shows they are from 
are less popular?  No!  Or because less people 
watch anime?  No, not that either!  So, I'll 
have to assume that it is linked somehow to the 
fact that so many shows are now CG....

Now to the question at hand-  if you think about 
what I've just said, I think that two things 
will eventually happen- One, the value of 
Dougas, Gengas and Rilezu will go up, (because 
if they are all that are available, they would 
become more collectible), and two, the value of 
cels will go back up, maybe even higher, 
because, like I said, there will still be as 
many fans of the shows, but cels from them will 
be harder and harder to find...

What do you folks think?