I would normally hate the idea of duo winners, but honestly Arunita really deserves something this season. As you pointed out, as Sayli gains popularity she will primarily eat into potential Arunita votes, so it will be an uphill battle regardless for Arunita to be declared a solo winner.
For the amount of TRP she's helped generate for the channel and her memorable performances, I'd rather she get declared as a co-op winner than not be a winner at all. I really do think Pawan is going to win either way, so I'd rather atleast Arunita get recognition as a duo winner. How the show could/would spin that into reality, who knows
the million dollar question would be - will Sayli make the Top 5. She has to beat off the likes of Danish, Sawai and Ashish for 2 slots. She may eat into Aru's votes but her own struggle for votes is still there. She is by no means guaranteed a top 5 slot as of now and most voters have by now selected someone or the other. Let's see.