I get the Disney Rewards newsletter. The one that I still see on my desk (I tend to stockpile them) says Spring 2014. I think its basically a quarterly newsletter with Spring/Summer/Fall/Winter issues. Its a nice little "magazine" but I certainly wouldn't rely on it for early discount notices, its usually pretty much all after the fact information. The magazine will usually have your Disney Rewards balance printed on the first page as well (although usually a month or so out of date).
With regards to Disney Visa discounts. I believe that the norm is that Disney Visa holders, generally thru email, will receive prior notice of an upcoming discount, be it room only, or package or
free dining. As a general rule Disney Visa holders get an early booking window, as the offer becomes a general public offer usually 3-5 days after its first available to DV holders.
I don't think Disney Visa gives you any unique room/package discounts, just primarily an early booking window.