A few months back in August 2017, you may remember that a script for a new series was announced, tentatively titled "Scooby-Doo! Guess Who?". However, the tweet which pictured the script was deleted, calling into question whether the next series would be titled "Scooby-Doo! Guess Who?" However, Grey DeLisle-Griffin (the voice actress for Daphne) has just confirmed a brand new series on the Speech Bubble with Butch Hartman podcast. Around the 0:30 mark in the video, Griffin mentions that the new series is indeed called "Guess Who, Scooby-Doo?" (notice the slight title rearrangement).
It also appears that my prediction in this February 2018 post was correct. Though DeLisle-Griffin didn't officially call the series a reboot of The New Scooby-Doo Movies, she mentioned that the series will feature celebrity guest stars appearing in every episode to help the gang solve the mystery.
That's all that has been released on the series so far, but I'm sure more info and an official announcement will probably be coming soon, given that DeLisle-Griffin was allowed to reveal it on the podcast. I'm really looking forward to the series, and it will be interesting to see which celebrities end up guest starring on the show!