I honestly feel that the Pokémon franchise shows no signs of stopping or even slowing down whatsoever. Perhaps the most key indicator that Pokémon is not "winding down," so to speak, is that the franchise continues to sell phenomenally well. Practically speaking, the only reason to discontinue a successful, extremely lucrative franchise such as Pokémon would be if the creator himself felt as though he was running out of ideas and wanted to halt the series of his own will - yet interviews with those in charge of the creation of Pokémon display no such pessimism. There are ultimately no visible signs that the series will end soon.
The fell omens spelling the end for Pokémon have been going on since the first generation. People have constantly spoken, since the franchise's early years, of how Pokémon doesn't sell well and can't continue to innovate, yet the fact remains that it has. Shortly after Yellow's release, I read on a website that Gold and Silver would not make it to the United States because of lack of interest - but they did, and they were extremely popular. Shortly after Crystal's release, I read a report saying that - and I quote - "it's safe to say that this is the end for Pokémon" - yet Ruby and Sapphire came out and met with phenomenal success. (I'm sure there were similar thoughts circulating before Diamond and Pearl's release, but I can't remember any. XD)
Ultimately, one of the main problems is that we, as consumers, underestimate the producers of Pokémon. We assume that, just because we can't think of any new ideas, the creativity of the producers must have run dry, as well. Ultimately, however, the creator of a franchise will often have far more expansive ideas which have been shaping since the franchise's birth than consumers can possibly fathom; this holds especially true for Pokémon. Many people have stated in the past that the creator of Pokémon had devised more than one thousand species before the release of Red and Green. As farfetched as this sounds, my research indicates that this assertion may be more accurate than people commonly believe. In the original days of English Red and Blue, when ridiculous rumors of secret Pokémon spread like wildfire, I incessantly researched and tried to determine the validity of these rumors. In my research, I happened across some compilations of concept sketches of Pokémon from Red and Green. Many of these showed first generation Pokémon in earlier, less detailed forms, such as a Lapras without a horn and a more juvenile Seel without the muzzle or exposed tongue. Among these, however, were images of new Pokémon I had never seen before, such as a roly-poly blue mouse, a pink creature looking like a cross between a fairy and a bulldog, and a round reddish mouse covered in fluffy fur. As I later discovered, many of these Pokémon appeared in more detailed incarnations in Gold and Silver. The blue mouse was an early sketch of Marill, the pink creature was an early Snubbull, and the red fluffy rodent was an extremely early concept of Cyndaquil. There were other early sketches as well, including Chikorita and Qwilfish in strange-looking forms, but this proved that many Pokémon were created far in advance of the games in which they debuted. More recently, it was revealed in an interview that Shellos was originally intended to be in Ruby and Sapphire. Furthermore, not all of these sketches have actually yet even come into existence: I recall that a baby form of Tangela, known tentatively as Monjii (Tangela's Japanese name is Monjara) was originally planned for Gold and Silver.
The fact that many Pokémon that were created long ago are just now appearing in games lends credence to the idea that, when people say that the older Pokémon were better, they may be speaking purely out of nostalgia. We tend to remember the events of our past in a rosy hue, and our fond memories of the earliest Pokémon no doubt embellish their presence in our minds. In fact, in speaking about Pokémon with young children who did not grow up with Red and Blue but whose first exposure to Pokémon was with Diamond and Pearl, I have found that they cannot tell the difference, stylistically, between a Pokémon of the first generation and a Pokémon of the fourth generation.
Something we have to consider when evaluating anything is that our assertions will always be inherently biased. There is no avoiding this, yet there is no shame in it, as we cannot but help reflecting ourselves into everything we say and do. Nothing humans say can ever be truly objective. This monstrosity of a post I've just made certainly isn't objective, and you can tell a lot about the way I feel and think just by reading this. It is important, however, when trying to evaluate something as objectively as possible, to take into account the views of others rather than just forming evaluations from our own perspective. I have often heard people assert that Diamond and Pearl were uncreative because they had too many "useless" Baby Pokémon or that there are too many "useless" Bug-types. The fact remains, however, that not everyone perceives these Pokémon as useless. I am always extremely excited about new Baby Pokémon and often fill my team with them (half of the Pokémon on both my Japanese Diamond and Japanese Pearl teams are Baby Pokémon, in fact). Their stats may not be the best, but they are not so low as to render the Pokémon unusable in battle (I know from experience). Looking beyond stats and raw data, however, the Pokémon themselves have cuteness and other stylistic elements that appeal to people such as myself; not everyone raises Pokémon based on raw stats, and many Pokémon scorned by those focused entirely on winning wireless battles are beloved by those with a different philosophy on Pokémon. Similarly, I don't feel that the abundance of butterfly, moth, and Normal/Flying bird Pokémon is a bad thing: in fact, I like it, as it represents the same sort of biodiversity found on Earth. While many people would say that all birds are alike, a passionate birdwatcher would feel that even a chickadee and a goldfinch are too intrinsically different to be lumped together in terms of behavior and qualities. Likewise, even Pokémon who seem extremely similar are often very different, both in stats and moves and in stylistic quality.
Well, I've blabbed on long enough. In short, I feel that the fifth generation will see the same degree of wonder and innovation we've come to expect from Pokémon. Aren't I the optimist. XD