Yes it was possible to bring more from west of the Curzon. But even Kresy still had a lot of Poles left. Just look at Soviet 1959 census.BTW, do you think that more Poles from west of the Curzon Line would have settled in the Recovered Territories in the extremely unlikely event that Stalin, for whatever reason, would have allowed Poland to keep the Kresy after the end of WWII?
I think the scenario in which Stalin would have allowed Poland to keep all of the Kresy was extremely unlikely.
However, the scenario in which Stalin would have allowed Poland to keep some part of it, was quite probable.
For example, he could have adopted the principle that post-war Poland's area = pre-war Poland's area. In this scenario he would have had to allow Poland to keep ca. 78,000 square kilometers of land east of the Curzon Line. For comparison, adding Lviv alone is just 9,300 km2 extra (area highlighted in the map below covers only ca. 9,300 km2):
If apart from Lviv you add also Grodno, the combined size of these two areas is ca. 10,500 - 11,000 square kilometers.
So even with Lviv and Grodno within Polish borders, post-war Poland would still be much smaller than it was in 1939.
Grodno was awarded a medal for brave defense against the Red Army in 1939, so the loss of it was painful to Poles.
Soviet "Blitzkrieg" against Grodno in 1939:
The panorama of the city: