When pre-purchasing something, especially software, there is ALWAYS the chance of it being delayed due to unforeseen complications.
It's a fact of life, and it's not limited to ED or RAZBAM. There are hundreds, if not thousands of games that have been delayed in the past due to bugs, extra features or whatever.
Same on steam. I myself had pre-purchased The Witcher 3 and it got delayed. I didn't mind, because I'd rather have a product being delayed rather than have it full of bugs.
If you dislike the fact that there is a delay involved when you've already paid for the product, then it might be best if you do not pre-purchase at all.
I'm not saying this to insult you or anything, but if you get annoyed by certain situations, then personally I think it's best if you try to avoid getting into those situations in the first place.
That said, RAZBAM has done an extraordinary job keeping us up to speed with the development with loads of screens, teasers, information. Hell, they even released a WIP of the manual for crying out loud.
They've given more than valid reasons for the "delay" (if you can even speak of a delay, I don't think so). They said it'd be available mid-December, and eventually adjusted it to December. So far, they're still well in the clear.