Around 30% is a ceiling after which he will have to start eating his liberal competitors to gather up some more.
Why does he need to gain more? All the polls are showing the same story - that if Trzaskowski scores 30% and Duda scores ~40%, then it's going to be much harder for Duda to find votes in the 2nd round than Trzaskowski. Even Marcin Palade (well known PiS-sympathiser and political scientist, but a fair one) is making it clear that Duda can only rely on 20-25% of Bosak's votes in the 2nd round, while Trzaskowski will pick up 30-35% of them.
For Trzaskowski, there's nothing to be gained by attacking other candidates. Biedroń tried to attack Hołownia and failed. Hołownia tried to attack Trzaskowski and failed. Why would Trzaskowski make the same mistake, when he could just reach out to their electorates after the 1st round, especially given that there's not much sympathy for Duda among the electorate of the other candidates?
As for Trzaskowski speaking - he seems to have done pretty well to get 1.6m signatures in 5 days, especially given that no other candidate managed it in 5 weeks.
The whole battle will take place over the center and undecided voters and Duda have more qualities to win them.
However, it's not that simple. He has two choices - he can either try and win over the centre ground, or he can go full radical and try and win over Bosak's electorate. Either strategy is dangerous, yet he needs to win one of them convincingly. The electoral mathematics are the same ones that caused PiS to lose in the Senate - they ignored the threat from Konfederacja and ended up losing the Senate as a result.
Interesting note: four debates are planned now.
Newsweek - 15.06.2020
TVP - 17.06.2020
TVN - 19.06.2020 (possible change)
Polsat - 22.06.2020
The Polsat one will be the one to watch.