"I'm waiting for you Saturday morning at 6" doesn't make sense. You can say "I will be waiting for you... "or "I'll wait for you" or "I will be there waiting for you..."

Maybe it is an axception but there is something about using pre. continues tense for future; http://www.edufind.com/english-grammar/present-continuous-future-arrangements/

When you say "I'm waiting for you" it means now at the same moment. ( present continues tense) But if you wanna refer to the future. You should use "will" and be careful!! after will comes the infinitive. For Example: I will wait for you Saturday morning at 6. You can't say " I will waiting for you. If you wanna use the verb in the future continues tense you should add "be" . For example: I'll be waiting for you Saturday morning at 6. Hope this would help!!! Have a great day.

I think if it is quite sure you will wait for one, you can use pre continuous. If you just decided to wait, future would be better.