Normally, as a believer that military operations end when they reach thier logistic limit, I’d be inclined to believe that the Soviets were unable to assist the Poles. Rokossovsky’s armies covered hundreds of miles and participated in two major offensives, Bagation and Lvov-Sandomierz. Bagration had played out and other than grabbing a few bridgeheads in areas that were lightly defended, the Soviets were stopping at the Vistula. Repairing the road and rail network behind them, and getting supplies and new equipment to the front, wasn’t going to get done before the autumn rains. So for all practical purposes, the gigantic Soviet summer offensive is over on this part of the front.
However, what Stalin did at this point is proof that despite thses limitations, he welcomed the opportunity to watch the pro-western Poles and Nazi Germans kill each other. The fact that he incited the uprising, did absolutely nothing to help, and blocked Anglo-American attempts at help issufficient proof that he used this as an opportunity to exterminate potential anti-Soviet elements in Poland. He would have done this anyway, but this way he got Hitler to do it for him.
If Hitler had been a little more broad-minded, he could have used this situation as the one real chance to split the alliance arrayed against him. He could have withdrawn from the immediate area of Warsaw and allowed the Poles to set up their home government. Even better, he could have allowed safe passage of the London Poles to Warsaw to take over, forcing the Brits to recognize them as the official government. Can you imagine Stalin’s reaction to a hostile Polish government, recognized by Great Britain, interposed between his armies and the Germans? What do the allies do when the Poles deny access to the Soviets, as they probably would?
The diplomatic situation between the UK and USSR was dicey enough over the Polish Question. Had Hitler taken adavantage of it, it offered the only real chance to split the Grand Alliance and salvage something other than total defeat.
Hitler knew the Poles would never go for that.
Ironically, one of the men Hitler most admired was Marshall Pilsudski. Even attended his funeral. And when the Nazis invaded in 1939, he had them send a guard detail to guard Pilsudski's tomb. In the early days, Hitler envisioned perhaps having Pilsudski as an ally against the Soviets, knowing full well of Pilsudski's hatred for all things Russian. Although by all accounts of the man, it would have been hard to imagine Pilsudski agreeing to be partners with Hitler.
One reason the Nazis opposed the Poles so much, was because of their racial theories, they surmised that since many Poles had at least some Germanic blood in them, that they would be a formidable foe, and therefore, unlike the other Slavs, that they considered untermenschen and didn't stand as much of a threat, the Germans genuinely saw the Poles as an enemy that had to be wiped out, or else they would always pose a threat to the Reich. It also explains why the Germans never allowed Poles to work as guards at the Death Camps....give a Pole a rifle, and the first thing they'll do with it is shoot the German.