It is true that Nisekoi has become subjected to the downside of being a weekly publication - due to the popularity of the manga, it's being extended longer than it's (most likely) intended run to capitalise on volume sales. I can't even remember the last time we had a chapter dedicated to the whole lock-key thing, but that isn't to say that I'm no longer enjoying the series. But it has basically devolved into an ecchi-less To Love Ru. However, if the anime ends at the point in the story where I think it will, it will be at a point before it drifted off (and actually at one of the high points of the series).
In regards to the anime length, even after the Romeo & Juliet play, there is still enough of the main story to fill another season of similar length -
but that's where I would leave it. If I were Aniplex, I'd end season 1 with the play as it's not an anime-original ending so it leaves some room for continuation, but is still a nice place to stop. Then, when the manga nears its end, I'd do another season of a similar length that trims the fat and ends with the manga conclusion. (Of course, this is all depending on if Aniplex can do another season - I can't imagine what the budget of the Nisekoi must be and I hear that estimated volume 1 pre-orders are low).
In regards to the love situation, I personally think it could go either way at this point. I mean, Chitoge is obviously the main focus as her joining the school is what kicked off the series and the one-shot did end with her being the girl, but in every character popularity poll so far, Onodera has been on top (and hell, thanks to Y-san, Tachibana beat Chitoge in the recent one - Tachibana was shown in the pre-release info and on the official site, so she's not a spoiler) and the author has outright admitted that how often a character appears and such is affected by their popularity. There is also a lot of speculation that there's another promised girl, as the number of key-bearers at the moment is one less than in the original story. I'd say that the only characters who have feelings for Raku but have no chance are Tsugumi and possibly Haru.
I do agree that Chitoge will most likely be the winner, but I would love the author to give us a surprise with Tachibana xD.