If you can wait then wait. If the model hasn't been updated by the time your academic year ends, you could always try and use your discount since technically the new academic year would not have started. Apple are well known to be lenient and give a little lee-way on things like this. Also, you could purchase just as your year ends and if the new one comes out within 14 days you can return your just-purchased model, get the refund and then order the new updated model again. Apple tend to have a 14 day return policy, no questions asked.
The yet to be announced new model will undoubtedly be "better" than the current model but the current model will be a good computer for several years yet. And even if you waited, 10 months later Apple will still bring out a newer model. No matter when you buy, the certain fact is that sooner or later a "better" machine will come out; just depends on how much you value having the latest model for the longest length of time.
With regard to the yet-to-be-announced new iMac, you might want to consider the following:
No Mac Pro model has been announced and the line may even come to an end this year. If the line dies, are Apple going to bring out a beefier iMac to cater to that market? Would you be interested in that?
The rumours are rife of a new form factor MacBook Pro coming out this year that has a similar look to the current MacBook Air, essentially losing it's DVD drive. If this is the case then the new yet-to-be-announced iMac may also lose it's current DVD drive. This I think is a real possibility. Is the current included DVD drive important to you or would you be happy to have to purchase the current Apple external DVD drive?
If the new iMac loses it's DVD drive then that paves the way for the inclusion of either a second standard (non-SSD) internal hard disk or beefier components to satisfy those that might otherwise have purchased a Mac Pro. Also bear in mind Apple are pushing Thunderbolt EXTERNAL storage options which also play to the killing-off of the current Mac Pro.
Of course all of this is just my own speculation but when you look a little deeper there are a lot of considerations to weigh up.
Look on the bright side though; if you buy now and an "uber" upgrade comes in the next four months, you only have to wait another few years before you upgrade to a newer model that will trounce this years yet-to-be-announced iMac
