I think this link title is misleading. This isn't a revision of JSON but rather a revision of JSON Schema, a language for writing grammars that can be automatically validated.
JSON itself would not have if statements under this proposal, and indeed the syntax of JSON wouldn't change in any way.
Thanks, title changed from "JSON draft 07 supports if/then/else" which would have been a shocking development.
This seems like a step in the wrong direction :/
I think this would be a very harmful change to JSON, but fortunately it turns out to be a change to JSON Schema, where it shouldn't really be a problem. (I think it's not a langsec concern because I think the same kinds of parsers should be able to validate data against these grammars with or without the if statement... depending on what kinds of state can be used in the condition, maybe.)