No, you do not. In fact, you can register for a Ph.D. in Information Technology at the same time as you register for an MS in Telecommunications.
Students who graduate with an MS in Telecommunications degree are eligible to apply for other tertiary degrees. Their ability to enter such programs will depend, as in other Master's or Ph.D. programs, on a number of factors, such as the Grade Point Average earned within their MS in Telecommunications degree program and the alignment of the MS in Telecommunications courses with the courses proposed to be taken within the higher degree. A GPA of at least 3.5 in the MS in Telecommunications program should enable a student to move on to a Ph.D. in Information Technology at GMU or to the MBA program, here or at another university.