From what I can tell, the projections are that the ruling party will receive the most votes, but not the majority vote. PiS only has slightly more than a third of the votes, while KO has slightly less than a third.

The current exit poll results seem to indicate a 37% - 30% - 11% - 10% - 9% vote division, with PiS leading with 30%. If the other parties band together against PiS, the biggest party by percentage will end up as the opposition.

Visualised, this looks like this:

Koalicja Obywatelska is opposed to PiS, that’s kind of their entire point. Lewica, the leftmost party, also won’t exactly partner up with PiS. Trzecia Droga is supposed to be an alternative to either large party, but if they work together with the left wing parties, the three of them have the majority. I don’t expect the right-wing Konfederacja to partner up with the other parties.

The votes are still being counted and the more right-wing remote areas appear to have reported their votes earliest, so the balance may still shift back and forth a bit. It’s technically possible the left and center parties can’t make a deal and PiS remains in power together with two other parties, but the news articles I’ve read find that rather unlikely.

Oops that should be ruling

By forming a coalition.

If the ruling party has 35%, the largest opposition gets 30% and there are some parties aligned with the opposition, they can easily get over 50%, thus being able to form a government.