What would've happened to Russia had it not entered WWI?

[Muhler]

I think it was inevitable Russia would end up in WWI.

Russia was seen as the big threat to Germany in particular, but also Austria-Hungary.
Russia's industrial growth was at the time the largest in the world, in percentage way more than Britain and USA. Russia was going from a backward agricultural country to an industrialized nation - which is of course why Germany saw it as a military as well as economic and political threat. And why Britain eyed Russia with some, shall we say, skepticism...

As such it was almost inevitable that Germany and Austria-Hungary on one side would clash with Russia. - That would also lead to war with France, due to the treaties, but not necessarily with Britain. Even though I'm certain Britain would secure the Channel and the French northern ports. Britain was not interested in seeing a German navy anywhere near the Channel and I think Germany may have held back, in order not to provoke a war with Britain.
One of the reasons why Britain did enter WWI was the von Schleiffen Plan, where the German armies would march through Belgium.
Belgium being the key country in Europe in regards to armies marching east and west.
Further south is the Rhine, making east-west movements difficult. And even further south is the dense Schwarzwald and the Alps. So armies had to march through Belgium, or any war between France and Germany would end up as an indecisive border-war. Especially due to the fortifications that had been constructed along the border.
So the best way to ensure peace in Europe was for all major nations to guarantee the Belgian neutrality with military force. I.e. the first country to march into Belgium, would be at war with everybody else.
It worked for 40 years.

Another thing is that it was by no mean inevitable that the murder of Arch-duke Franz-Ferdinand would lead to war.
Apart from a penal-action towards Serbia, there was little appetite for war in Austria-Hungary. But for all sorts of reasons things got out of control...

The interesting question is: What if the outbreak of WWI had been postponed? Say to 1920.
Russia as an industrial power would have been stronger. There were well-overdue plans for improving the Russian infrastructure, enabling the Russian army to be not only better equipped but also better supplied. (The Russian logistics was the biggest obstacle for Russia fighting efficiently. A somewhat incompetent general-staff didn't help either!)
Also, the Russian Baltic Sea Fleet had not been fully rebuilt after the disaster in 1905, by 1920 it might, posing a direct threat towards Prussia.

Politically, by 1920 Lenin would still have been sulking in Switzerland, while Stalin would likely have been executed as a bandit or ended up in Siberia. That the Communist didn't have a strong leadership in place, might have meant that the Russian unions might have followed a path similar to the unions in central Europe. I.e. more peaceful, but still influential. Especially if a Social-Democrat party would have had time to establish itself in Russia, due to the growing urbanization and industrialization.

So provided fairly modest political reforms had been made, there is IMO very good reasons for thinking that that the Imperial Family would have been secure by 1920.
So with a Germany that had plenty to do fighting France on the border, a part of it's navy being held back, just in case Britain entered the war and fighting against a much stronger Russia, WWI might have been shorter and ended up in a stalemate, before the casualties became so disastrous that it led to revolutions.

So IMO there is good reasons for believing the Russian Tsar would have survived a postponed WWI (which by the way, would not have been a world war, but a major European war) for at least a few decades more.
Whether it would have evolved into a constitutional monarchy, with curbed political power, or would have been toppled at the next European war, say around 1950, is of course another matter.

[Curryong]

Considering the attitude of the Tsar and his wife (who had enormous influence over Nicholas) to the already very limited political reforms in his reign, why would it be seen as feasible that this couple, who believed implicitly in autocracy, would allow more political rights? In my view that scenario would have been extremely unlikely. For various reasons I believe revolution was inevitable in Russia since the 1820's. There was a brief window of opportunity in Tsar Alexander the Liberator's later reign for some genuine strides forward towards a truly democratic system of government. After he was assassinated hope for that was lost IMO.

[Muhler]

I agree that major reforms were inevitable. The Tsar would have been forced to accept political changes. If not he would be outed, one way or another. He may have been an autocrat and not the sharpest knife in the drawer but he did accept changes during the war.

So the alternative would have been political changes or being abdicated. These changes happening before the war between Russia and Germany (being the main contestant) broke out.

There were AFIAK little genuine political pressure for getting rid of the monarchy. Limiting it's power, yes, very much so! - As indeed there was in most European countries at the time.
The Russian Revolution IMO came about as an extreme form of reforming a system that was already being reformed and very much weakened due to a disastrous war. Without that, a full-scale revolution may not have been necessary. And keep in mind, that it was far from certain to succeed.

So all in all, I think the chances of the monarchy surviving such political reforms and a fairly limited war would have been better, than the chances of the monarchy being abolished.

While I think WWII could have been avoided, I don't think that was possible with WWI. (Or more correctly a Great War).