anxietyismyname:
1. Last year, the invitation came in as late as Jan 22nd so I wouldn't discount the possibility of hearing from the adcom at the end of January. But FYI, a fair number of round 2 applicants have already received invitations.
2. As far as visiting Cornell, I think it should've happened before submitting your app. It's not like the adcom will slip in "oh, he/she visited today" note into your folder upon your visit. And most of all, unless you live in upstate NY, going to Ithaca especially in January is difficult. In my memory, greyhound from NYC to Ithaca took 6 hours, given that there is no breakdown.