Updated July 24, 2018: Following the full reveal of this as part of a promotion for a Weirdworld-centric arc of Champions, series writer Jim Zub clarified the temporary nature of this costume:
Just to clarify-— Jim Zub (@JimZub) July 24, 2018
This costume is just for the Weirdworld story we're doing in Champions from October through to December. https://t.co/itB5DJbQsW
Original Story: A drastically redesigned Miles Morales will debut in October's Champions #25... and he may not even be called Spider-Man anymore.
The fourth Champions #25 teaser released Monday features the Ultimate universe refugee redesigned in a more medieval-type garb - with Marvel's filename simply referring to him as 'Spider.'
All three teasers have featured the text "Change the World?" and "Weird..." leading us, at least, to speculate this could be concerning Weirdworld, which was re-introduced in Marvel coninuity back in 2015's Secret Wars and featured itermittently since then.
Champions #25 is scheduled to be released this October. Look for Marvel's full October 2018 solicitations later this week on Newsarama.