I have to agree with Art Cernosia. I also agree with Professor Weber's prediction that §504 will be seeing more action because of the IDEA eligibility tightening.
The sad truth is that public schools have long seen §504 and IDEA as the same thing and indeed the federal regulatory scheme for P-12 is similar to that of IDEA and often permitted the application of similar eligibility criteria - even though they were never meant to be precisely the same. §504 was always meant to cover a broader swath of children with disabilities, including those who needed less in the way of "special education" but more in the way of accommodations. Just to confuse things, the IDEA and §504 shared terminology with some of the services/interventions that would not be required under 504, such as certain therapies.
The exhaustion requirement is also a significant barrier to a pure §504 claim. However, a pure §504 claim does have its place. For example, §504 would permit a claim against a physically inaccessible school environment. That's not within the purview of impartial hearing officers to remedy. Similarly, retaliation claims can proceed under §504. Moreover, as more and more school systems declassify children for IDEA purposes and opt to serve them under §504 instead, those schools will be hard pressed to claim a failure to exhaust administrative remedies of a law by which the schools just said these children were not protected. One can only talk from both sides of one’s mouth for so long...