The start of Apex Legends' first season saw the introduction of a new character, Octane—and one more character will arrive before the season is over, according to Sony's website.
Sony's Apex Legends PS4 page says that "two new characters will launch over the course of the season", one of which is Octane. One new weapon will also arrive during the season and launch with a "full set of cosmetics to unlock", Sony said. The season is set to last around 12 weeks.
"Two new items" will also make their way to the game in that time—I presume one of them is the jump pads linked to Octane, so we can expect one more item soon.
Apex Legends datamines have previously revealed apparent details of eight new characters. Most leaks have paired Octane with a character called Wattson who uses a Tesla Trap ability, so she's the most likely candidate to arrive soon.