Do you think the Uchiha's would have been succesful if Itachi hadn't killed them?

[Shadow Phantasm]

Not really as both sides would have weakened each other to the point where the other villages would attack, so the Uchiha were screwed other way.

 

[Lilt]

I think the Uchiha thought they could because they were depending on Shisui and Itachi.

However, those two were never going to betray Konoha.