A list of apparent upcoming LEGO sets is circulating online and through other LEGO Fan Media, originating from Libreriatilos, a Spanish retail store. This includes what some fans believe may be a future Collectible Minifigures series, themed to LEGO Marvel.
As reiterated by Just2Good and Ashnflash, one of the products listed on the Spanish online store shares its set number with that of other LEGO Collectible Minifigures series. The price listed is also around the same as would be expected for a single foil pack.
Of course, these are only rumours and nothing is confirmed until the LEGO Group officially announces it. However, if this particular set listing does turn out to be true, it is currently unknown whether it would be themed to Marvel comics like most of the 2021 LEGO Marvel sets or to the Marvel Cinematic Universe.