He likely isn't expecting to die. However he is the long term planner Sith Lord. Plans within plans. If we consider how much Darth Vader fears this man, we are expected to think he is far more powerful and thus Luke can't just fight him a win. He looks defenseless. And that is part of his ploy. At any time he can call on the Force to stay Luke's hand, or electrocute him. Vader, MUST obey his master. That's fear right there. And from what we saw in previous OT films, Vader was the one to be feared. But someone he fears, and is even less forgiving that Vader? This man is scary.
Palpatine's goal is to get Luke to fall to the Dark Side. He figures that once this happens Luke will crave power and join the Emperor as the only one who can complete his training in the Dark Side. Luke, if he does kill his father in a rage, falls to the Dark Side. He might attempt to kill the Emperor, but discover that he can't. If he manages to fuel his rage and hatred, he will just become more a servant of evil, as Yoda put it. Eventually, the only option left to Luke, for a short term solution to the problem at hand (saving his friends), is to join the Emperor. That is the only way left to save them if he can't defeat the Emperor. And even that won't really work. Palpatine might (might) call off his troops and let the Rebels escape, just so they can be used later on to twist Luke even more into the Dark Side. Eventually setting it up so Luke has to kill them, directly or indirectly in his efforts to defeat the Emperor with the Dark Side. The Sith apprentice's goal is to learn all one can from the Master and then kill the Master to become the next Master. Palpatine knows this. He's trying to gain an apprentice that is worthy to follow him. Palpatine will someday die (unless he can find a way to cheat death), but with a properly powerful Sith Lord to eventually replace him.....he wins for the Sith Empire. Luke Skywalker, Dark Lord of the Sith, eventually gains enough power and knowledge to overthrow Palpatine....but is so deep into the Dark Side that he will retain power, control over the Empire. It will be too late.
Unless Leia still lives....Hope will have died in the Galaxy.