You can wait 27 days then come back here and ask if you should wait again.
The fact is, what is available today will run exactly what you need it to run I presume. You didn't exactly outline your needs so one can only assume.
If you were asking about say a Mac Mini, which hasn't seen a true update in ages then maybe that question would be a bit more understandable. The only thing I think people are going to say is that the ACDs are in need of an update. I disagree in that it does exactly what I need it to do as I don't need any extra inputs for my gaming consoles or anything like that. However, if they do update the current displays and they come out looking like the iMacs I'd be slightly annoyed myself.
My advice to you is that if you don't need anything now then go ahead and wait the 27 days. If you do then buy it. You won't be disappointed.