What a revolution may be is discussed in this post, The Clash, Revolution Rock.
But what makes this song interesting is how it challenges the ideological beliefs of the political supporters the Beatles might have had. It appears to be John Lennon saying “count me out” for efforts at political change back in the late 1960s. Waiting to see the plan before going with it, and intoning that it’s gonna be alright, could be considered conservative, status quo and establishment-oriented.
We wouldn’t necessarily put Lennon in any of these categories, but politically, the song is thus cautiously practical – even radicals should have an idea of the reasoning and potential consequences, of their slogans and political demands?
Maybe the Beatles were being idealistic in assuming that revolutions, which tend to come with violence, should not be the go to option. Such pacifism should still have been considered in accord with the commonly held views of most hippies back in 1968.