Firstly, gen 5 has a sequel, so gamefreak WON'T repeat that. They will make the third gen, or at least a third game like a sequel
Secondly, every gen has 3 games. Gen 1 don't count cause it don't have legendary mascot. Gen 2, lugia and ho-oh is a duo, but they have to put suicune to mascot. Gen 3, gen 4 have 3 games. Gen 5 has two sequel, but basiclly it ACTUALLY ONE GAME, cause Kyurem has 2 forms so IT IS JUST LIKE A THIRD GAME (sequel is about Zekrom, Reshiram from Black, White, not about Kyurem, so it BASCILLY A THIRD GAME). So gen 6 will have a third game
Thirdly, MORE GAME MEAN MORE MONEY, gamefreak have to make more to earn money.
First of all, we don't
know whether GameFreak will revert to making a third game as a director's cut of the first two games in a generation or it will continue to make sequels (Generation V, after all,
was a reset of the entire
Pokémon franchise.) Second, the number of games that GameFreak releases in each generation actually varies quite a lot more than you would think; here, let me show you what I mean with an impromptu chart:
Generation I (4 games:)
Pokémon Red Version (There were two versions of this games: the first was released only in Japan, while the second one was a version that GameFreak made for the USA release of the
Pokémon franchise and which also included the improvements from
Pokémon Blue Version)
Pokémon Green Version (Japan only)
Pokémon Red Version (USA edition, merged Japanese version with improvements from Japanese
Pokémon Blue Version)
Pokémon Blue Version (Japanese director's cut and third version/USA counterpart to
Pokémon Green Version
Pokémon Yellow Version: Special Pikachu Edition
Generation II (direct sequel to Generation I, 3 games:)
Pokémon Gold Version
Pokémon Silver Version
Pokémon Crystal Version (director's cut and third version)
Generation III (first series reset, 5 games:)
Pokémon Ruby Version
Pokémon Sapphire Version
Pokémon FireRed Version (remake of
Pokémon Red Version with improvements from
Pokémon Blue Version added in like in the original USA release)
Pokémon LeafGreen Version (remake of
Pokémon Green Version with improvements from
Pokémon Blue Version added in)
Pokémon Emerald Version (main-series games' director's cut and third version)
Generation IV (5 games:)
Pokémon Diamond Version
Pokémon Pearl Version
Pokémon Platinum Version (director's cut and third version)
Pokémon HeartGold Version (remake of
Pokémon Gold Version with improvements added in from
Pokémon Crystal Version)
Pokémon SoulSilver Version (remake of
Pokémon Silver Version with improvements added in from
Pokémon Crystal Version)
Generation V (second series reset, 4 games:)
Pokémon Black Version
Pokémon White Version
Pokémon Black Version 2 (half of first paired sequel to be released within the same generation as its prequel counterpart)
Pokémon Black Version 2 (half of first paired sequel to be released within the same generation as its prequel counterpart)
So, as you can see, the number of games has varied between 3 and 5 across the generations; in fact, I wouldn't be surprised to see another generation have
6 games (2 original main-series games, 2 main-series sequels, and 2 remakes) some day. Finally, I can
prove the following statement that I made in response to your ignorance about the first two
trio leaders not only with the links to
Bulbapedia that I included in that post, which I have quoted below, …:
Actually,Generation II was a little bit different…:
Ho-oh rules over the
legendary beasts Raikou, Entei, and Suicune as that
legendary trio's
master, and
Lugia similarly
leads the
trio of
legendary birds (Articuno, Zapdos, and Moltres) introduced in Generation I.
…but also with an attached picture from that same source. Think about that, would you?