Mainline Pokemon games are known to build upon many prior entries' features, offering something new yet recognizable. For example, Pokemon Sun and Moon introduced regional variants, which were later introduced in Pokemon Sword and Shield and are planned to appear in Legends: Arceus, making this a staple of the series moving forward. Future generations are likely to keep on adding new things that will build upon the series' legacy, but there is a lot of room for improvement in terms of what sort of trends continue and which ones change.
Among them, there is a specific trend that has continued in every mainline Pokemon game except Generation 2: including a pseudo-Legendary Pokemon that is Dragon-type. The Dragonite evolution line began this trend in Generation 1, and the only other exception was Generation 3 where the Salamence line was accompanied by another pseudo-Legendary, Metagross. Generation 2 was the only one to feature a non-Dragon Pokemon as its pseudo-Legendary, and that was Tyranitar. Considering both Tyranitar and Metagross' popularity, leading to them receiving Mega Evolutions in Generation 6, maybe it's time for Generation 9 to not feature a Dragon-type pseudo-Legendary.
Why Pokemon Games Don't Need More Dragon-Type Pseudo-Legendaries
Pseudo-Legendary Pokemon are considered among the best of each Generation because they pack great stats across the board as well as unique designs in three stages of evolution. Yet, while Dragon-type Pokemon might differ between one another based on their secondary typings or the region they belong to, they all share some typical design elements like a long tail and other physical characteristics. Pseudo-Legendaries are often not available until mid- to endgame, and they are all very powerful in their own way, so having them always be Dragon-type Pokemon can be limiting.
Up until Generation 6, Dragon-type Pokemon were among the strongest because of their many resistances and few weaknesses, only succumbing to Dragon-types and Ice-types - most of which could easily be dealt with through Fire-type moves. Generation 6 introduced Fairy-type Pokemon, which became instantly popular due to their designs, strength against Dragon-type Pokemon, and their solid resistances when blended with typings such as Water. Dragon-type Pokemon were immediately put at a disadvantage against Fairy Pokemon because they took double damage and could deal no damage with their STAB moves (not counting any secondary types).
Fairy/Steel-Pokemon like Mawile gained a lot of traction within the community because Fairy-types are normally weak to Steel and Poison, which are both made redundant by Steel-types being resistant to Steel and immune to Poison. Dragon-types, on the other hand, started to lose popularity following to the introduction of Fairy-types, yet they remained commonly found even outside of Legendary Pokemon and pseudo-Legendaries. There are a total of 76 Dragon-type Pokemon total, considering regional variants, Mega Evolutions for Pokemon that weren't Dragon-type prior, and other Pokemon forms.
With Generation 9, the Pokemon series should start including more common Dragon-type Pokemon earlier in the game, and then feature pseudo-Legendaries that explore other type combinations. A great way to do this would be having each new Generation's pseudo-Legendary Pokemon take an unused type combination, and then make it more accessible in future games when new pseudo-Legendaries with other unusual combinations are released. This would make pseudo-Legendary Pokemon even more unique like Tyranitar and Metagross, as well as more appealing for all Trainers. More importantly, they would bring much-needed variety to the game, even if they happen to be Dragon-types with secondary typings like Bug, leading to a type combo that doesn't exist yet.