No there is a season 5, its still in pre production with no other info but the show does NOT end with season 4 part 2 which releases in July and is 2 episodes like you said. Season 5 was confirmed a long time ago and is currently the final season.
The big reason for the splits this year (BCS, Stranger Things) is Emmy cutoff for 2022 is May 31st and the VFX etc was not done for part 2 so they split it. They've already said stranger things season 5 will not take 3 years but release sooner but also have a time jump. There have been HUGE hints the past 2 seasons of time travel being involved, like all the back to the future references last seawson and the Upside Down being frozen at a specific date and time (Will's entrance) in this season. That was years after Vecna entered too so thats an important clue.