Haven't heard about Rondo stage planned or Ch12 slot.
Hmmm, it would make sense if they were saving the 12th Chapter for when PSN version releases, then release that Chapter for both versions once PSN is up to date with DLC.
I wonder if they could add more stage slots if they wanted to. But it might be harder to patch than simply using premade slots for extra stages.
Well Chapter 10 is super awesome having all Castlevania 1 stages united like that. Well yes, only Simon's size fits with the enviornment, but it's still one of the best stages of all time and fun with all characters and it's just so massive and packed with lots of rooms and great level design that surpasses metroidvania level designs. The classic Castlevanias really knew how to better balance platforming, traps and stuff better for more danger and more variety in topography, although metroidvanias were better with how locations can connect into a bigger world and more non-linear progression. So Chapter 10 possessing a combination of both generations of level design flavors is really superb! 
Also Chapter 11 even though it isn't Castlevania based, still is related to Castlevania in a way because many agree Getsu Fuma Den is like the Japanese culture inspired version of Castlevania. Also Chapter 11 has two of the most awesomest tracks remade in supreme excellence!
Also the enviornment and mini-bosses add a lot of variety! Castlevania characters do fit nicely in those 8-bit enviornments and add great feeling and entertainment unlike anything else! It just goes to show there are no walls within true art. 
RoB stage and Ch. 12 slot were talked about on GameFAQs.
Romulus knows just about everything there is to know about the game. He figured out
Fuma was going to be in the game a month or two before he was even announced.
But as for the 8-bit stages, it goes along with what
Uzo said before. He talked about inconsistency, and that just made it worse. Don't get me wrong, I loved Ch. 10 (again, didn't really play 11). I loved the way they managed to connect the stages (they flipped the outer area of Stage 4 around, though). But there were so many other areas that people would have preferred seeing in the game. I would have liked a stage using the outer areas of
OoE, rather than almost the
entire game take place in the castle once again (note I said
almost).
I agree with the stuff about Getsufuu Maden, though. That whole thing is what even got me playing the original game in the first place, and I enjoyed it. But still, over
Fuma, I would have preferred the planned
Hammer or
Albus. But I can't really complain, since I kick so much ass as
Fuma. ^.^ But let's just hope that
Ham-ham or
Albus will make it into the PSN version.
Also, I would have liked a
Simon's Quest style stage, with a day and night cycle. With at night, enemies get stronger. But one can only dream about this stuff...