The Germans didn't really have plans for a defeated Russia prior to the war; for their intentions during the war, one need look no further than the [Treaty of Brest-Litovsk] (https://en.wikipedia.org/wiki/Treaty_of_Brest-Litovsk).

As to 'superpower' status, Russia had the fifth largest economy in the world in 1914, and it was still growing. However, much of this was based on French and other foreign sources of capital, and it's growth was also accompanied by great instability, namely the rise of Polish and Ukrainian nationalism, as well as the growth of socialism in Russia, demonstrated most explicitly by the 1905 Revolution.

Just to add to what /u/DuxBelisarius already said, that France provided Russia with massive amounts of capitol after the 1894 Franco-Russian alliance. This capital proved to be vital aid for the Tsarist Regime after the 1905 revolutions and the Russo-Japanese war which took a huge toll on the Russian economy. The investment was also a key part in Russia's industrialization/modernization, things like the building of the Trans-Siberian Railway in 1891 were helped in large part by French funds. Economically at least Russia was on the up on and up, along with the growth and modernization came unrest as evidenced by the Lena Goldfields and the strikes that accompany it. The growth of Marxism and other opposition groups show that modernization and growth came partially at the price of stability.

Militarily however I think the Germans did view Russia as a 'superpower', Russia had a massive army, which in turn gave rise to the idea of a Russian steamroller that could prove to be unstoppable. Russian and French troops outnumbered German and Austrian troops by over 1 million in the run up to the war (can't remember where I got these numbers). In reality however Russia was weaker then it looked as the fighting in WWI would prove. It had a small amount of shells at the beginning of the war, and despite Russia having a massive army, many of the recruits were poorly trained and were lead by poorly trained officers. Russia also had poor railroads, which hampered their mobilization efforts and their efforts to move reinforcements and supplies to the frontline. Their pre-war planning was also generally lacking. Russia's defeat in the Russo-Japanese war shows many of these key military weaknesses which were not fully rectified by the time WWI began.

The idea of Russia as a 'superpower' is tenuous in the run up to WWI, there were many strengths but probably many more weaknesses and large amounts of instability in late Tsarist Russia which hampered its ability to persecute a successful war effort in 1914, ultimately leading to Paul Miliukov's criticism about Russia's war efforts "what is this, stupidity or treason?".

Hope this helps!

Sources: The Origins of the First World War, Controversies and Consensus by Annika Mombauer .

Russian in the Age of Modernisation and Revolution, 1881-1917 by Hans Rogger.

Two important factors that spring to mind were (1) the French investment in Russian railways and (2) the Russian rearmament plan.

In the years leading up to WW1 France was investing a significant amount of money in Russian railways. This was significant to the Germans as the planned railway expansion would significantly reduce the time it took to mobilise the Russian army. As you probably know, the German plan for WW1 was to focus on knocking out France before Russia could fully mobilise. However, once the planned (French funded) rail lines were complete, it was theorised that Russia would be able to be fully mobilised a mere 2 days after Germany (Collapse of Empires: The war on the Eastern Front 1914 - Prit Bruttar). If true, this would negate the German strategy.

At the same time, Russia had launched a massive rearmament programme that would improve the quality of Russian arms (particularly artillery) and reduce the German material advantage over Russia. This was scheduled to complete in 1917.

A structural perspective on the war says that Germany had no choice but to start the war when it did. England was weakening (relative to Germany) but Russia was growing incredibly quickly with help from the French. The theory says that Germany had to attack then because its allies Italy and Austria and the Ottomans were in decline, and they would have no hope fighting a mega Russia and still powerful britain .