Hiroyuki didn't let me down, Nagisa made Saki swoon with her speech this chapter and next week will probably pave the way for the clincher.
I also have a feeling that whatever Nagisa says next week will set the stage for Shino either being welcomed in or bowing out. Maybe Nagisa will say something like "I want us girls to get closer"?
Overall though, I think whether we have three-timing or four-timing all hinges on whether Naoya is philosphically "right" to stop himself from falling in love with Shino. Because mutual love has always been emphasized. I think it's more arguable that he's not wrong to do so for Mirika, because Mirika is determined to work against his relationship with the other girls. But arguably, he could decide that it's okay to love someone even if that love ends unrequited, which case he might theoretically fall for Mirika and then pressure her to accept his love.