Overall, Lucas has made close to $3.8 billion with DVD sales (http://www.statisticbrain.com/star-wars-total-franchise-reve...). This is one of the reasons why Star Wars movies are not available on iTunes and other VOD platforms.
Putting those titles on Netflix would decrease their value. Netflix would have to pay big money for that…
Disney has been providing Netflix content for their streaming service probably since day 1. I remember when it first launched, I believe Lost was available on the server. All 6 seasons are available and have been since the series finale.
The future for entertainment is not physical media that you can buy. It's much easier and quicker for me to switch my TV to my Roku box, load up Netflix and start a movie than it is to switch to Bluray, and wait for it to load and show previews. I can't remember the last time I purchased a DVD/Bluray that wasn't in the bargin bin for $2, but we watched Netflix just last night.
I don't think Disney is going to lose out on Star Wars sales if they start streaming it, there will always be people that want to buy the package so when the internet is off, and all they have is a portable DVD player, they can watch Star Wars, but by making this deal with Netflix they are only increasing their profits, there is no devaluing going on here.