There is a section in the agreement which pertains to restrictions on a Marvel retail development, apparently planned at that time. Without looking the text up again (and I'm certainly not an expert anyway), I don't think it said anything about a restaurant or similar venture, though I have no idea of that means a cafe would or would not be permissible.
From everything I think I understand, it appears there is nothing stopping Disney from using in the Florida parks any Marvel character which Universal either isn't using, or else is using but only in an incidental manner.
Of course, it was only a joke anyway.