Of course it is, but remember his inner reason for rejecting Ayumu? That he has his hands way too full right now taking care of Nagi to consider getting a girlfriend?
By design, Nagi is the default girl without a doubt. I even remember an interview with the mangaka where he outlined that initially he planned to resolve the "Hayate confessed to me" misunderstanding early, and then wanted to develop the romance from there. That does not mean that it HAS to end this way (I'd say it's evident that the mangaka is very much aware that Hina is hugely popular and a cornerstone for the story), but it means that for a SUCCESSFUL Hina ending alot of loose ends need to be tied. Here, resolving Nagi is key.
We shouldn't be fooling ourselves, the day Hayate seriously commits to a girl, the show is over. Hina confesses, Hayate accepts, Nagi lets go, "happy ending"? Nope, no go. Something else needs to happen first - Nagi realizing her own delusions, and preferably developing a credible alternative. Here, Himegami is the wildcard which _might_ give the mangaka a cop-out if he ever decides to REALLY give Hina an end run.
Keeping fingers crossed that Hina popularity remains high enough to convince the mangaka to alter the story's course for real
