Interesting. Yeah, I don't see a 2018 Sport Hybrid either. There's no news of it being discontinued anywhere I can see, but neither do I see the 2018 Sport Hybrid for sale anywhere.
According to this page, the Sport Hybrid is available with either the Technology or Advance package, although it appears the Acura site doesn't offer it on their build page. I think the carsdirect.com page you're looking for is
http://www.carsdirect.com/acura/mdx-sport-hybrid , but the Price It New button takes you to the 2017 page. Weird.
This page mentions the hybrid only contributing to about 5% of sales, so maybe Acura silently dropped it due to lack of sales? Or maybe the 2018 model year won't start until the calendar year 2018 for Acura? *shrug*