We have never gone during the summer so I can't compare, but there were a couple times in MK that were much worse than we have experienced previously, even worse than the one time we went during the spring break season. We had friends get stuck at the MK bag check/entrance for an hour one morning at about 11:00am (we were walking from BLT so thankfully we had a separate entrance and got in very quickly). I hope 2018 will be better, but if anything I think it may be worse, based on the dates alone, and what I have seen for DVC availability (I know not a great predictor but this is the worst I have seen in 8-9 years for availability). Personally I am planning on a lot of resort time until at least the 6th or maybe at least avoiding MK.