Another Kirby game to come out. It appears and acts similar to Return to Dream Land and Triple Deluxe. I've been noticing a trend with these games which I think is bound to continue for quite a while. Warning, minor spoilers
For starts, the Copy Abilities act much like their Super Star (Ultra) incarnations, and non-Super-Star Copy Abilities and new Copy Abilities replicate this. Each game has at least 20 regular Copy Abilities and adds at least three new ones to the roster. Return to Dream Land was Leaf, Whip, Water, and Spear. Triple Deluxe was Beetle, Bell, Archer, and Circus. Planet Robobot is Poison, Doctor, and ESP. "Old" abilities that were added in Return to Dream Land were Spark, Needle, Tornado, and High Jump. In Triple Deluxe, Wheel. In Planet Robobot, Jet, UFO, and Smash [Bros.] Even Dream Collection re-added Smash.
Each game's levels have alliteration and spell out something in particular, with these games hinting at the final boss (Crowned, Flower(ed), and Program). Another element in the game were Super powers. In Return to Dream Land, Super Abilities. In Triple Deluxe, Hypernova. In Planet Robobot, Robobot Armor. These are also used in the defeat of the final boss. Furthermore, each game has an Arena, a form of extra mode which utilizes enhanced bosses and mid-bosses (with unique suffixes; EX, DX, and 2.0), a True Arena, and surprise bosses, with at least one Meta Knight-esque fight (Galacta Knight, Dark Meta Knight, Mecha Knight).
Each game has a form of collectible that progresses the game in some way. In Return to Dream Land, Energy Spheres (although only the first was required to progress). In Triple Deluxe, Sun Stones (with Keychains as a bonus). In Planet Robobot, Code Cubes (with the added Stickers). Each game also houses 2 sub-games (excluding the Arenas), with at least one multiplayer oriented one. In Return to Dream Land, Ninja Dojo and Scope Shot. In Triple Deluxe, Kirby Fighters and King Dedede's Drum Dash (with only the former being multiplayer oriented; also extra versions). In Planet Robobot, Team Kirby Clash and Kirby 3D Rumble (also with the former being multiplayer; also both enhanced later).
Along with all of that, little bits of nostalgia here and there. HAL Rooms, Moon Doors, older Copy Abilities, 8-bit references, music (Kirby GCN trailer music for Return to Dream Land, and other remixed themes for the other games), goal game, old bosses/mid-bosses returning, such as Mr. Frosty, Blocky, Grand Wheelie, Whispy (in various degrees), Kracko, Dark Matter, Galacta Knight and Dark Meta Knight, Masked Dedede, Drawcia and Dark Nebula (as Stone Statues), HR-D3, Nova(?). The list can go on (give me some more if you can).
Whatever main series Kirby game comes next after Planet Robobot, it's probably going to take on a very similar formula.