It makes sense for the cop universe to be just Singham, Sooryavanshi & Simmba because the storyline is clearly building up towards a mulitstarrer movie in future. That's why these cameo appearances are happening in Sooryavanshi. I see this move being Akshay Kumar's biggest grosser but I don't know if Singham 3 will happen after Golmaal 5.
As far as Simmba goes, I only watched this movie for Ajay Devgn's cameo appearance. That one scene helped the WOM and got audiences talking in the mass circuits. Bit of credit goes to Ajay's contribution based on what I said in my second. Apart from that, It was a good film I guess.