Not only were there Incline hikers, last year, as there will be this year, but they were/are again incentivized to be there by the Incline being closed for MONTHS, starting the day following the Marathon.
Still, at my pace at least, slightly under 9 hours, I wasn't much affected. I may have changed course slightly to go around a few, and some came around me, but there weren't a lot, and I was certainly not impeded. But it is best to know there will be some there.