The short version, from publisher Zuxxez PR director Joerg Schindler: "The Temptation had been canceled due to technical outdating [sic]. We use a complete new engine for Two Worlds II."
Dirk Hassinger, who runs U.S. publisher TopWare, gave the full story:
"After Two Worlds the dev team started an add on," Hassinger wrote. "Later this was too huge and became a full product (Two Worlds: The Temptation), but in the last year as the development went forward, we found the technology outdated and started a new engine generation from the scratch. Now it is a real Two Worlds II with state-of-the-art technology. Of course some ideas and story partly developed in the last couple of years, which could have been a part of Two Worlds: The Temptation (PC/360) and Revelation (PS3), will be used for 2WII, but it is for sure a different title and not a simple rename."
Well, there you have it. Is it weird we want to play it even more now?