Rumor has it the next 2 worls Decade will travel to are:
The "Shinken no Sekai" and the "RX no Sekai."
In RX no Sekai, he will meet RX, and apparently in the Shinken no Sekai, Decade will meet up with the Shinkenger. Rumor also has it on the Shinkenger side that the Decade characters will appear in Shinkenger, involving something about Kaito wanting the IkaOriGami as the treasure of the world.
Awesome news if true. The first, ever, Sentai-Rider crossover.
Update:
The Shinkenger crossover seems to be PR for the movies, (makes a lot of sense) and seems to happen in late July. The trip to RX's World seems to be episodes 31 and 32 of Decade, which seems to be the end of "2nd Chapter" rumored of Decade. After these 2 episodes, W should take over.
"Chapter 2" is actually episode 20 and onward.
Episodes 20-30 (and possibly 31, 32 with RX) are known as Decade: Chapter 2.
The following is supposed to happen:
-Yuuske is killed
-Otoya appears, and transforms into DarkKiva, fights with Decade (confirmed)
-Natsumi meets with her high school friends about something important (confirmed)
-Decade achieves a new form during his fight with DarkKiva (Complete Form, confirmed)
-Diend will Kamen Ride Decade
-Decade's cards turn black, and Natsumi now sees in her dream, 2 Tsukasas, one who will kill the other
-The reason that Diend has the ability to use cards Decade has aqcuired from the worlds, is that all the cards are added to the same repository. Anything Decade has, Diend has too...