When Thor was last seen in the MCU, he was a god without a path. Having mostly conquered his demons and proved himself still worthy of wielding his mystical weapon Mjolnir, he helped to take down Thanos and his forces during the finale of 2019's Avengers: Endgame.
When Dr. Jane Foster was last seen in the MCU, the astrophysicist was in England doing research when she was reunited with Thor. In Avengers: Age of Ultron, it was established that the two were dating, but in Thor: Ragnarok - about two years later in the MCU - Natalie Portman doesn't appear as Jane and it's explained that she and Thor broke up.
Portman was announced at SDCC 2019 as a returning member of the Marvel Cinematic Universe, returning as Jane Foster with the additional powers of Mighty Thor in 2022's Thor: Love and Thunder.
A new set of casting calls for stand-ins and photo doubles have been listed on Starnow (via Thor: Love and Thunder News on Twitter). The site lists the calls for a "major feature film" that's being produced in New South Wales, Australia. Given that Thor: Love and Thunder appears to be being filmed in the Aussie state, these listings are very likely for the MCU film.
The first call is for a male, aged 18-40 years old, about six-foot-four, with blonde hair and a muscular build. That sounds an awful lot like Chris Hemsworth's Thor.
Further lending credence are the next two casting calls for stand-ins for two female characters. One is Caucasian with long, blonde or brunette hair and stands about five-foot-three (which is very likely for Jane Foster)
The other is intended to stand in for an African-American actress who stands from five-foot-four to five-foot-seven and has an athletic build (most likely Tessa Thompson's Valkyrie)
Additionally, there's another casting call looking for a variety of people who stand at five feet or below.
WHAT THIS MEANS
Stand-ins are used all the time in Hollywood productions, being used to stand in place of actors so the crew can get the lighting and cameras configured correctly before shooting.
While it's pretty clear that the three photo doubles in the first casting call are for Thor, Jane, and Valkyrie, it's not as clear as to what the actors under five feet are needed for. However, they are needed to shave their heads and be comfortable wearing prosthetics. This seems to suggest that fans will be seeing some type of alien species in the film itself.
There have been a wide variety of unique characters who have popped up in the Thor films, many of which do have a wide variety of heights and builds, so it shouldn't come as much of a surprise that the production is seeking people who may be a bit shorter.
The Taika Waititi-directed film is expected to get production rolling in early 2021 and will release on February 11, 2022.