pingpong wrote:But, why would he say that he will be in touch with me ?
Because he's interested in having you as a grad student. But unlike us of the hyperactive physicsgre.com checking ilk, a professor's idea of elapsed time in measured in weeks. HIS deadline, after all, is August when you report to campus.
EDIT: I think a reasonable guess when a professor spends time to contact you is that you have a very good shot of getting in. You don't need a long conversation before the admissions process--I'd only contact him again without him first instigating if you somehow end up seeing a rejection email in your inbox, to ask whether or not he's willing to speak to admissions on your behalf.