He says,

كَلَّا سَيَكْفُرُونَ بِعِبَادَتِهِمْ ...

Nay, but they will deny their worship of them, (on the Day of Judgement).

... وَيَكُونُونَ عَلَيْهِمْ ضِدًّا ﴿٨٢﴾

and will become their adversaries.

This means that they will be foes in a state other than what they think about these gods.

This is similar to Allah's statement,

وَمَنْ أَضَلُّ مِمَّن يَدْعُو مِن دُونِ اللَّهِ مَن لاَّ يَسْتَجِيبُ لَهُ إِلَى يَوْمِ الْقِيَـمَةِ وَهُمْ عَن دُعَآئِهِمْ غَـفِلُونَ

وَإِذَا حُشِرَ النَّاسُ كَانُواْ لَهُمْ أَعْدَآءً وَكَانُواْ بِعِبَادَتِهِمْ كَـفِرِينَ

And who is more astray than one who calls upon, besides Allah, such as will not answer him till the Day of Resurrection, and who are (even) unaware of their calls to them And when mankind are gathered, they will become their enemies and will deny their worshipping. (46:5-6)

As-Suddi said, كَلَّا سَيَكْفُرُونَ بِعِبَادَتِهِمْ (Nay, but they will deny their worship of them),

"This means their worshipping of the idols. ''

Allah said,

... وَيَكُونُونَ عَلَيْهِمْ ضِدًّا

and will become their adversaries,

contrary to what they hoped for from these gods.

As-Suddi said,

"They will be in severe opposition and argument.''

Ad-Dahhak said,

"This means enemies.''