Gible is the dragon-type pseudo-legendary from the Sinnoh region. It is very hard to come by, as all those dragon-types have a pretty low spawn rate.
To make up for this, Niantic typically holds Community Days, which have featured rare Pokémon that spawn in large numbers for a three-hour period. The Shiny versions of Pokémon usually launch with their respective Community Day and the Shiny rates are dramatically increased during the event period. Since Gible’s Shiny form is launching ahead of its expected Community Day, players are now concerned that it won’t get a Community Day at all.
Garchomp, Gible’s final evolution, is a pretty good ground- and dragon-type attacker, but outside of players who might live near a Gible nest, very few players have one. Even players with stacked Rare Candy are unable to get a Garchomp simply because they can’t find a Gible to begin with.
Based on patterns, the next Community Day in January would be for Piplup, with Gible possibly following that in February.
Pikachu had its Shiny form released before its event, but it was also the first ever Community Day in the game. Niantic does like to break patterns away from what we’ve seen. Last year had the Lake Trio, a set of three Legendary Pokémon, appearing the wild, which was a first for the game.
Polygon has reached out to Niantic for clarification on Gible’s Community Day (or lack thereof).