While we haven't seen exactly how Dish plans to integrate the Assistant into its receivers, the company does say that it'll provide visual feedback as well as audio responses, which means you can do things like have it show your Google Photos on your TV. You can also ask for things like news and weather which will show on your TV, and your connected smart home devices will work with the Hopper as well -- assuming they are compatible with Google Assistant, of course. (Chances are better than ever that those devices will work with Google, in case you were wondering.)
Dish also told us that you'll be able to control the your TV through the Assistant, as well, despite a press release that made it sound like you'd have to use Dish's separate voice services for controlling content on your receiver. Somewhat ironically, Dish has worked with the Google Assistant for months now, just in a slightly different fashion. Starting in June, you could talk to your Dish receiver with the Google Assistant via a Home speaker or the Assistant app on an Android phone or iPhone.
Update, 1/9/18 2:00AM: This post has been updated to clarify that Google Assistant on Dish receivers will control all TV content as well as work with Google's services.