Spoiler (mouse over to view)
in the latest chapters, Agata's imouto fell in love with Bossun and even confessed but he ain't giving an answer yet.
well, Sket Dance basically a comedy manga just like Gintama, the romance part will never overwhelm the comedy. The only possible love interest for Bossun is Himeko anyway, I'm hoping for a twist but it's not likely to happen unless Himeko's kicked out of top 5 popularity poll.
If you want Sket Dance with more romance, grab Hayate no Gotoku!