I asked myself the same question, but I think they will not be added. When the iPad Pro came out, they immediately added their simulator. Actually, I think it was in beta version of Xcode 7.
For these new devices, the iPhone SE has the same resolution as the iPhone 5S. This is also 64 bit, and they both do not have 3D Touch. I assume that there is a simulator iPhone 6 and 6s, because the latter has 3D Touch, unlike the former. The new iPad Pro is almost the same as the iPad Air 2.
In conclusion, it does not really matter;)