https://www.cbr.com/avengers-4-spider-man-lego-leak-spoilers/

In the new Spider-Man movie, there will be a quartet of supervillains with elemental powers.

Apparently, two of the members will be Hydro-Man & Molten Man.

We don't know yet who will be the Air & Earth Elemental villains.
Sandman seems to be the obvious choice (too obvious ?) for the Earth Elemental.
Mysterio (// "Mist") could be the Air Elemental, except if they want to use one of the minor Spidey villains (Cyclone or Bora) or if Vulture comes back as the Air Elemental ...
I don't know if villains such as Grey Gargoyle, Moses Magnum or Whirlwind can appear in a Spider-Man movie.

IMO, not only this team is a prototype of the Sinister Six but also it is a combo between the Frightful Four and the different teams of Marvel Elemental supervillains :

- Elementals(1974)
http://www.marvunapp.com/Appendix/elementl.htm

- Elementals of Evil (1979)
http://www.marvunapp.com/Appendix/rokkorrs.htm#Elementals

- Elementals of Doom (1981)
http://marvel.wikia.com/wiki/Elementals_of_Doom_(Earth-616)

- Force of Nature (1991)
http://www.marvunapp.com/Appendix4/forceofnature.htm

To sum up, yet another concept intrinsically linked to the Fantastic Four will appear in the MCU (or in this case, the Marvel+Sony shared sub-universe) even though the FF themselves won't appear.