Given their email on the subject consisted solely of a Shelter-esque image and the words "Come one. Come all!" there's not much to go on but I figured enough people were fond of the series that this was newsworthy.
I have also come up with some theories as to what the teaser is actually teasing:
1. Shelter All-Stars.
This would be a MOBA featuring your favourite Shelter characters like That Badger Cub You Tried To Leave For Dead But The Game Wouldn't Let You and That Mysterious Predator Which Snatched That Other Cub In The Night and The Rabbit That Got Away From You When You Were A Lynx Mother That Time. Just look at them all on that hillside, poised to go into battle and use their spells and stuff.
2. Shelter But You Play As The Meadow And Have To Nurture Baby Meadows
This would be a slightly more complex reworking of the franchise's fondness for examining one particular trophic level and have you play as a sort of abstract conceptualisation of a whole ecosystem spewing out seeds and attracting insects and drawing nutrients from their inevitable decay. Expect many YouTube guides for how to optimise the nitrogen fixation process and whether or not picnicking teens are a nuisance or a feature.
It's just a meadow. The team like meadows and have drawn a picture of a meadow and written "MEADOW" on it. The animals are there to be an appreciative audience for the meadow and are thus a framing device rather than a sign of any potential gameplay or narrative. Further emails may include "COFFEE" and "NEW SOCKS". Maybe even "THAT THING WHERE YOU WAKE UP EARLIER THAN NORMAL AND GET A LOT DONE".