Just chill. We were selected for YC interview last year and we talked/emailed/skyped with partners only when we were selected for interview. I believe teams start talking with partners only when they are accepted for interview.
That said, best of luck!
Incidentally both Gates and Jobs started their companies sans YCombinator.
Anything's possible (you could add mark z to that list). It's about validation, resource allocation and probability.
Getting accepted to yc (or even interviewed) is indication that at least a few capable people think you and what you're doing are worth something and that you're headed in a good direction.
There is a limited amount of capital, public exposure (press) and face-time with angels/VCs/worthy advisors to go around. With YC, you get a leg up in getting access to these resources.
A YC company (historically, and for the above reasons) is significantly more likely to at least get to the next stage of funding and growth (actually employing people). Since everything involves luck, anything that improves your chances is a big deal.