The future tense of can is CAN! It does not change. Your sentence in correct format will be: "I can be there." To make it more specific that you are talking about the future, you can add a time. For example: I can be there tomorrow/ I can be there at 4:00...etc. Just for your information: it will sound more natural to say those sentences in a different way. That is: I will be able to be there (tomorrow/at 4:00...etc.) Hope you can understand my explanation! ^_^

You would either say 'I can be there tomorrow'. or 'I'll be able to meet you there tomorrow.' Usually can is used in the present tense. I can speak English. I can swim. In the past tense it becomes could. I could speak Spanish when I was a child. I could run really fast two years ago. In the future can becomes 'be able to'. I will be able to meet you next Monday outside the cinema. I will be able to speak Chinese next year.