I felt your sentence was much longer and not as effective as the original, but as a restatement of the original, it is fine. But there are still a couple of errors:
"The number of diabetes CASES will reach two times THE cases in developing countries (delete "than"_ AT present in the next thirty years."
Please note that diseases are not countable, so we could never have " two diabetes" or "The number of diabetes" without a noun ( "cases", " patients" ) following