According his own writings;
At the Second Party Congress in the summer of 1903 I represented the Siberian Union together with Dr. Mandelberg. Once the Congress split into the Majority and the Minority I joined the opposition which had later developed into the so-called "Menshevism". At that time I published in Geneva a brochure by the name of "Our Political Tasks". But as soon as Menshevism started to formulate its tactics, in the sense of advocating that the proletariat coordinates its actions with the political bourgeoisie during the period of our "bourgeois" revolution, I broke with the Mensheviks and stood outside both factions.
After the 9th of January, when the popular movement started in Russia I travelled illegally via Austria to Kiev and St. Petersburg.
http://web.mit.edu/people/fjk/essays/Trotsky-bio.html
So, Trotsky doesn't see it yet as the opportune time to travel back to Russia with no "Bloody Sunday" unrest...yet...
It seems likely to me that G. S. Khrustalev-Nosar would remain the president of the
St. Petersburg Soviet of Workers’ Deputies for awhile longer. With the unrest lessened, he'd be less at risk of being arrested. IOTL, Trotsky only became president of the organisation after Khrustalev's arrest.
Lenin was in disagreement with Khrustalev's ideas IOTL
http://www.marxists.org/archive/lenin/works/1906/jul/04.htm
When Khrustalev is replaced it's probably by another Menshevik; Parvus.
Perhaps
St. Petersburg Soviet of Workers’ Deputies just fiddles around not getting anywhere for a few years, not having any strong leadership. The Russian Revolution - the big one - is delayed but nobody remembers Trotsky, and he returns too late to be of any relevance in the local power structure.