Yes, putting all efforts in improving tanks - that way would lead to a dead end. IMO, Germany would be simply enough to build more the best tanks it ever produced - Pzkw V Ausf. E and Pzkw V Ausf. F - "Panthers". Its high-velocity 75-mm main long-barrelled gun, with its fast reloading was a formidable weapon against all Russian mid tanks, and it also proved no worse for Russian JS-2 (in spring-summer 1944) when fighting from the ambushes and in skirmish battles where Germans excelled -everywhere where they coud shorten distance down to less than 1 km to make their Kwk-42 effective against front armor of JS-2s. The German industry also had to go on produsing Pzkw-IV whose technoogy by 1943 was very smoothly established. These Panzers still were a very good weapon.
JS-3 never took part in WWII athough Berlin saw them in May 1945 in victory parade.
The main point here is that putting efforts in expensive producing of more powerful tanks would - and my colleagues have pointed that out above - result in discrease of general tank-producing rate, and the Allies (including Russians) will have an upper hand with armoured forces in the battlefied. They had far more raw materials, more powerful industria base, far more human resources. They could substitute tanks and personnel at much faster rate than Germans, and if one would say that in such a condition Germans could do nothing but to emphasise the goality of weapons and personnel, I woud argue that generally Germans had both better compared to the Allies (including Russians) but by a very narrow margin, so risking into slowing tank-production in attempt to get something better was unjustified. I like the example of Japanese pilots whose training up to 1945 went in unchanged fasion, so Japan to the end of the war could annually produce only a imited number of qualified pilots. Americans like Russians adopted shortened course of preparing pilots. So what did the sides in Pacific had by 1943 after Pearl Harbor, Miduway, Guadalcanal? How many experienced Japanese pilots were still alive, with Japan unable to compensate losses as easily as the Americans. This holds true for German personnel as well. Quality of both the personnel and weaponry means money and time - and Germany had no such luxury.