So like...here's the thing. They may or may not get a "good" list of guests this year, but I can basically guarantee you that coming here and being all doom-and-gloom about it won't change anything. I get that you may be disappointed or worried but as someone who has organized events before (albeit on a smaller scale) seeing this kind of reaction from a potential attendee really doesn't do anything besides cause additional stress and grief to the event organizers.
I'm sure that the staff of Bronycon want to get the best possible list of guests they can, and want you to be happy. The reality is though that booking these guests isn't solely up to Bronycon -- the guests have to want to come and have the time to do so, and if etiher of those things are lacking (or if the guests can't answer until...after this day in April) then there really isn't anything that Bronycon can do about it. I seriously doubt that this has been caused by any kind of incompetence on the part of convention staff.
If you are really worried about it, just make as many easily-cancellable or low-risk preparations as you can and hold off on the more serious stuff for a bit. You can always decide for sure in a month or two.