I suggest you write what you leanred for. Some of the 1.5 topics need time to be learned in the right way. Since you will be ready for 1.4 only by 15th i dont think two weeks are enough to upgrade to 1.5. However if you can learn really fast you could give it a shot. Why dont you browse through the newer topics in 1.5 and have a feel for what it is like.