Exactly ... as ARDR is already a token that was distributed to NXT owners in 2016, there is no IGNIS airdrop for ARDR owners (that would have benefitted long-term NXT hodlers twice ...).

However, maybe it's not a bad idea, to increase demand for ARDR and improve the overall distribution of IGNIS tokens, to distribute the IGNIS coins that were not sold in the ICO to ARDR holders as an extra-official airdrop (But I don't believe that to happen).