cc6, in our school district (and state), when you have an IEP come up for the three-year review, ability and achievement testing is usually repeated as part of the process, unless parents and school staff agree there is no need to retest. In your case, I would think there are really good reasons to re-test. I don't know what typically is included (here) for the early IEPs given to preschoolers because we didn't have one, but once a child is 6, the ability and achievement tests (here) are WJ-III Cognitive and Achievement tests, in other districts they are sometimes the WISC for ability and WIAT for achievement. Basically, they are the very tests you'd want to have if you were paying for a private eval for gifted id. My ds is not on the autism spectrum, but I know a few other children in our district who were first identified as gifted through their IEP eligibility processes for autism.
The difficulty getting SLP help through the school district sounds extremely frustrating. Our ds also needed SLP help and didn't qualify. I wish I had some really useful advice! Please know I know how frustrating advocating for 2e kiddos is - sending you a cyberhug.
polarbear