Fear not Guardian! Those planets would surely come back! There is a video on YouTube by Unknown Player discussing about Luke Smith's response about the future of Destiny 2 (maybe even Destiny 3). [spoiler]In the post-credit cutscene, we see the Traveler spread its light towards our solar system, and then further outside our system. The ringing blast of light first hit the planet Mercury, then Mars, the Reef, then Saturn, and then outside of the Milky Way. This is a clue left behind by Bungie hinting that future DLCs may occur at these locations. [/spoiler]