Is this EU material? If so it ain't canon no mo.
Although technically we didn't see the Palpatine die in Jedi.
I would've loudly protested that before TCW since, y'know, Darth Maul was cut in HALF and somehow survived. (Aside: I liked Maul well enough, but he should've been dead and stayed that way.) But since TCW is "canon" and all that ... meh.
My whining on that note aside, yeah, we didn't actually see Palps die. I'm all but certain he did. After he fell down that chasm, the weird blue whistling-type thingies that surged back up was, at least in my four-year-old opinion at the movies, his "spirit" or essence in the Force giving out a last, good-and-pissed "ooga booga!" before he completely left the material world.
As far as Palps clones go, and even if we ignored the so-called new canon policy, I don't think the Emperor ever took on a cloned body until the "Dark Empire" series. I definitely don't think he ever assumed a clone before "ROTJ." Assuming he did, why did he look so fucking old, then?