1 You wouldn't believe what kind of comics they keep churning out of it. Or, actually, you probably would. Like giving rings in little boxes so she'd find about it when sinking and stuff. My personal favourite is where Yukikaze catches a bouquet.

BTW, all sorts of games have the "marriage" thrown in. It's usually a stats bonus. In Barcode Kanojo, for instance, "marriage" locks someone against being stolen, which may be useful if you have a personal favourite on whom you were throwing expensive DLC.

2 When the anime runs, it's gonna get worse.

3 "Worse" in what way? More tearjerker art than now? More new fans and new artists?

4 Worse in pretty much every way, actually.

5 When the Band Wagon gets going, that's always when it gets worse.
Kancolle is also a monster hit among the otaku.  It's going to be bad.
Only one thing: this is an original series, so it might not have the Hype + Failure problem from the opening scene.  The series could actually be interesting.  At least for top rotation fodder.

6 What?What's worse? Worse than what? What is the object of the worseness being discussed here? The "IT" that will get worse. Is it fan wank? Disturbing doujins? Too much steam in the bath scenes? To little?
Regarding Update: That hurt.

7 It's hard to imagine the anime doing much for the franchises popularity in either direction, at least in Japan anyway. Maybe in English speaking fandom it'll spike an interest, but given that I play KanColle as it is, I'll probably not notice a big difference in my circles at least.

As far as Arpeggio goes, the end-cards for most of the anime episodes already featured characters from KanColle, typically interacting with their Arpeggio namesakes. At the same time, towards the end of the run of the Arpeggio TV show, they did a cross over event in the KanColle game where you could, for a limited time, recruit various characters from Arpeggio and fight against the Fleet of Fog. I gather, from the folks I know who were playing at the time (getting registered for KanColle, particularly back then, is no easy feat!), Iona was hugely overpowered and helped many an Admiral through some maps which are particularly tough otherwise.