Recently, Henle has begun editing several of Scriabin's works - these are very new editions, put out in just last few years. I have the Sonata no. 7 which is fantastic and is simply leaps and bounds better than what else is out there (and what is there is few). The original editions of Scriabin's works I have found to be quite sloppy and sometimes confusing, just look through the Dover books of his works.I believe you can get Sonatas 6-8 and the op.11 preludes from Henle at this point, possibly more. Hopefully they will edit the op.28 fantasy at some point as well.
For some pieces of Scriabin I think Dover is fine. But I have sonata no.7 in both henle and dover, and I have to say the Dover edition of the piece makes it look like a nightmare. Not only is the typesetting ugly and clunky, but a lot of the rhythms look very confusing based on the way they are spaced - I also don't like the way the notes are slanted - it's just a personal preference but when I want to learn a piece of music I want to make that process as simple and easy as possible so I can start making music right away.
I'm learning this as well and I am using the Konemann edition which I checked out from the school music library, since it's no longer in print. Being a grad student, I get to keep it for the whole semester! I will probably be buying the Belaieff edition since I would like to have a copy of my own.