When the iMac gets update in the autumn/fall, it will not make any current iMacs (or even older ones) obsolete or dis-functional. If you buy now, your iMac will still work after the update.
Have you taken any look at any of the other dozen "iMac update" threads?
affect 1 |əˈfekt|
verb [ trans. ]
have an effect on; make a difference to : the dampness began to affect my health | [with clause ] your attitude will affect how successful you are.
effect |iˈfekt|
noun
1 a change that is a result or consequence of an action or other cause : the lethal effects of hard drugs | politicians really do have some effect on the lives of ordinary people.
2 ( effects) the lighting, sound, or scenery used in a play, movie, or broadcast : the production relied too much on spectacular effects.
3 ( effects) personal belongings : the insurance covers personal effects.