Nothing will change. Interest based advertising is made so that google hopes to offer better ads return for adwords users. As for adsense publishers, perhaps you'll have a little bit more clicks, or a little bit less, or just the same, honestly it doesn't change much to the clicking behavior of the visitors.
Not wont impact the publisher in anyway ! It is just about giving the advertisers more choices to select the theme of their business. This will help Google to further enhance the relevancy of the ADs which lacks sometimes.
This is untrue. In theory it should help the publisher because it should display advertisments that of interest to the person viewing a page. Only time will tell if it's effective or not. It might also hurt the publisher, because it could trigger a behavior where if your site is about Tennis and the visitor sees ads displayed about gardening and they may have been visiting gardening sites they may put 2+2 together and thing that YOU have done something to their computer and leave their site. The average guy doesn't follow Google and has no idea what this is about.
Interest based advertising will compete against contextual, placement options already available for the advertiser. It will be decided by the G bot to which ads will be published on your site to make you max revenue. However, it is too early to say it will benefit the publisher. For further reading read on Adsense official blog HERE