The problem with this in English is that "I do dance" suggests that I dance regularly. The only correct English rendition that makes sense here is "This time I AM dancing". Not "This time I'm dancing", as that omits the positive emphasis provided by כן. Not "this time I do dance" because that just sounds weird and un-English. Not "this time I will dance" because the Hebrew sentence uses present tense. The situation could be that I refused to dance up to now, but then the DJ put on my favourite song and I leapt onto the dance floor, saying "This time I am dancing."