Depends how badly you need it right now and what you're using it for. If you're just doing light photo editing then it doesn't really matter what model you have for example. There will probably be a new model in October or so, but if you really need one right now then go for it.
Yes they do! I set up a tracker as probably many do. They typically replenish the listings in the morning and end of day I noticed. They seem to only have certain configurations and I haven't seen any deviation from those. The 295s go first.
I ordered the 4GHz 16GB 512SSD M295X. Coming tomorrow--looking forward to it.
It will be a while before there is a refresh. I've however seen various good deals here in normal online-shops, which is usually a sure sign that something is in the pipeline. Though it could be a couple of weeks.
And even then: how much faster, better than the current model can the updated model be?
We're usually talking about a 10% or maybe 15% increase in CPU/GPU.
The iMac isn't the MacMini or the MacPro that get updates once every 2nd year (at best).