You'd still have the Left-Right split, but without Stalin's machinations it would drag on through much of the 1920's under the cover of unified communal government.
However without Trotsky the Left is the likes of Zinoviev, the Old Bolsheviks, although they will have great influence, the Right dominated by Bukharin will only grow stronger as time passes, as the policies of NEP and Socialism in One Country (both Right babies) will still gain great support.
Meanwhile the loss of Stalin and Trotsky means others will fill their gaps in the Politburo. The likes of Kalinin, Sergo Ordzhonikidze, Molotov would gain greater influence, however some key figures like Kirov, although strong moderates relied on Stalin to rise so quickly. I can see Kirov, left to run Azerbaijan for a while, turning up on his own merit in the late 1930's, a possible heir or threat to Bukharin. Similarly Kaganovich relied entirely on Stalin to gain what power he did, so he's possibly butterflied away entirely.
Regardless, I can see the few commited Old Bolsheviks being quickly outmanouvered by the growing number of 'young turks' arriving in the 1920s. Groups like the Democratic Centralists and the Workers Opposition who were supressed at this time could become major levers for influence and possibly save the CPSU from its oligarchic rule that led to the coups and purges more than anything in my opinion. I see Bukharin and the Right Opposition siding with the Democratic Centralists, essentially giving the Party as a whole greater influence. By the late 1920s, with the Politburo at least having to listen to the Party, I have little doubt they'd side with Bukharin, Tomsky et al on the Right because of there moderate and seemingly successful economic policy, no doubt taking liberities to bring up Lenin's ghost over the issue.