He's still alive, and now there is one less Sarlacc on Tatooine. He just felt like taking a swim, and his pure Spiral power was too much for the Sarlacc to take.
Later, when the Emperor is tossed into the bottomless pit, do you really think that's what killed him? No. Boba Fett was down there. And he wrestled the Emperor, causing several large explosions, which destroyed the Death Star. Lando just happened to hit the decoy core at the coincidentally right time.