It's a contentious issue among historians, as usual with any topic dealing with the red army, western historians take a dim view of the red army where as Russian ones take the more positive view of it. Both sides have some merit.

On the Russian side of things. The soviets ha just launched a major offensive that regained a lot of ground, known as operation bagration, and this combined with the fact that the Soviet Union didn't have the greatest logistical system, means that after such a major offensive it is logical that the soviets would not be able to continue fighting. And the soviets attempts to gain a foothold on the Vistula, which would be a necessary step to get to Warsaw, were beaten back.

Now for the western side of things. The soviets by the time of the Warsaw uprising already had a polish puppet government set up in Lublin to counter the London government, there was also polish communist troops fighting in operation bagration. The soviets told the polish home army that they would not tolerate differences between the Lublin and London governments (essentially telling them that the Lublin government was there preferred choice). The soviets also refused to allow allied aircraft to use soviet bases to supply arms to the insurgents. The polish home army had been promised support by the polish communists in exile, but it never materialized.

So, it's really up to how you interpret the events. For what it is worth, my opinion is that Stalin's signature realpolitik took over, he saw a chance to inflict damage both on his current opponent and a possible future opponent in the polish home army, who were obviously anti communist and politically dangerous.

Sources:

The Second World War by John Keegan

The third reich at war by Richard Evans