We know that there are different factions of the rebellion across the galaxy and the ones we do see mostly through the original trilogy is just one of them. It's not until Return of the Jedi where we do see the rebellion come together with all the different ships and factions to take on the Empire one last time.
Rogue One is coming out next year, and the movie will take place before A New Hope and will focus on how the Rebels stole the Death Star plans from the Empire. How will this connect with Rebels? Well we know that our group have been messing with the Empire for quite a while and by the time the events of Rogue One happen it would have been four years after the star of Rebels.
The rebellion, at the time it is now airing on Rebels is still in its early stages. You can see different factions coming together, but they are no where near the efficiency to start doing covert missions against the Empire.
We are also far off from big battle or wars happening between the rebellion and the empire but until that I can see more interactions with the empire.
In the context of the prequels, we actually get to see the development of the Death Star or at least seeing it in production. Because making a Death Star planet that size is going to take a long time to make so it would be cool to see it before it is finished in some form.
There is still that possibility that the series won't connect to the original trilogy, well at least not directly to it. We have already seen cameos from C-3PO and R2-D2 and some of the other characters that become relevant to the rebellion later on. But there is always a possibility that our group of characters will not become involved in the events of A New Hope, whether they are killed off or just travel to a different faction or become their own sorta ghost faction of the rebellion. Secret from everyone else, which could be cool and could keep the show going for a long time.
Do you think Rebels will connect to the original trilogy, if so how? or Should they even connect to each other?