Pokémon was an absolute behemoth back then though so it's not surprising that it will take quite a fall as Pokémon because less popular. I mean the R/B/G/Y games together sold around 20 million more copies than later main gen games would sell. It's expected.
This. I'm not sure why people are so surprised there is a drop in ratings this far into the Pokemon franchise.
The first gen games (and to some extent the second gen games) sold tons of copies and spawned the Pokemania. Part of the reason ratings were so high was because kids wanted everything Pokemon. Also back in the 90s more people watched TV in general since video streaming wasn't as easy as it is now. Once the fad died down during Johto we saw ratings drop from the double digits. It was inevitable. The fact that a series that was at one time a huge fad is still going strong way after all the hype and popularity is incredible.
The ratings today, although they may be only 1/4 of what the anime got in its prime are still extremely strong compared to most shows aired in Japan and around the world. Many shows would love to get the 4.0 ratings Pokemon gets these days.
There was a time when the highest rated shows had ratings
67.3 (I Love Lucy back in 1952-1953). There were other shows during that time made similar ratings as well.
In 2013 so far the show with the highest rating is NCIS with
12.3. The days where double digit ratings are the norm for shows is slowly fading into distant memory. This is pretty much across the board.
I'm not going to say that ratings don't matter because they do. Shows with good ratings get good time slots to ensure a maximum amount of viewers. They are allowed to take bigger risks and they get more support from the networks. And of course money. But Pokemon has good ratings when you consider the fad stage and the decline of people watching TV in general.
Can the anime change up its formula? Of course!
Will it make a difference in ratings? Who knows...