Pokemon GO is currently hosting Dragon Week Ultra Unlock 2020, which prioritizes the catching and collection of Dragon-type Pokemon. While this is great for players that like to train up and use these powerful Pokemon, there are plenty of other Pokemon types that deserve a special event as well later down the line.
Some Pokemon in Pokemon GO can and have taken advantage of holidays and real life events for special spawn events such as Ghost-types on Halloween. However, most Pokemon types don't have great calendar-based opportunities for events like that.
Keeping the fact that Pokemon from generation 6 and onward are likely going to be added relatively soon, more Pokemon of certain types will have more variety, better justifying type events. These are some types that deserve proper events in Pokemon GO.
Dark-Types
With the amount of times that Team GO Rocket becomes involved in Pokemon GO's events, it's surprising that there hasn't been an event completely focused on the catching of Dark-type Pokemon.
There are plenty of Pokemon that can have increased spawn rates during this event such as Murkrow, Sneasel, Houndour, Zorua, Absol, and many more that deserve some sort of spotlight. New Dark-based parties for the admins running Team GO Rocket could make for more additions to the event as well. They could also additionally introduce shiny versions of certain Dark-type Pokemon that previous didn't have their's in-game yet.
Fairy-Types
As mentioned before, Pokemon from generation 6 are likely to be introduced to Pokemon GO rather soon. Considering that Fairy-types were introduced in the Kalos region, more Fairy-types will also be added to the game as well.
With all this in mind, this would create the perfect opportunity to have an event that celebrates Fairy-type Pokemon and making their spawn rates go up. Other Pokemon such as Eevee could also have heightened spawn rates so that players can more easily obtain Sylveon, which is a Fairy-type Eeveelution not yet added to Pokemon GO.
Certain Fairy-types could greatly benefit from higher spawn rates such as Gardevoir and Togekiss, who both require high amounts of candies to completely evolve. Others such as Pokemon that will be added with the generation 6 update like Flabebe could help players catch more of the newer Pokemon when the update finally comes.
Electric-Types
Despite many events offering special hats for Pikachu, there haven't been any events focused on Electric-type Pokemon in general. Of course, there's no way that Pikachu would be left out of an electric themed event, but others would still get a chance to shine. There are plenty of eEectric-type Pokemon that require a lot of candies to evolve, so an electric-themed event would allow players to build up enough candies so they could be able to get powerful Pokemon such as Electivire, Magnezone, and Alolan Golem.
Possible event rewards could include special items such as magnetic lures or evolution stones for the Electric Pokemon that need them to evolve. A Pikachu with a hat alluding to other popular Electric-type Pokemon could work for it as a reward, such as a Raikou or Zapdos hat.
Pokemon GO is available now in select regions on Android and iOS devices.