Next Expansion Pack will have Pets in it and here is proof

[Rider]

<TraitList>
  <Name>Lazy</Name>
  <Description>LazyDescription</Description>
  <ShortDescription>LazyDescriptionShort</ShortDescription>
  <Hex>Lazy</Hex>
  <CodeVersion>EP5</CodeVersion>
  <AgeSpeciesVisible>Dogs,Cats,Horses</AgeSpeciesVisible>
  <Category>Physical</Category>
  <CanBeLearnedRandomly>False</CanBeLearnedRandomly>
  <ThumbFilename>placeholder</ThumbFilename>
  <ThumbPieMenu>placeholder</ThumbPieMenu>
  <ThumbDislikePieMenu>placeholder</ThumbDislikePieMenu>
 </TraitList>

This is found in the Traits.xml

As  you seen and as was told eslewhere that the next one is PETS, as you ss EP5, Dogs, Cats and Horses and probabley more.

[Claeric]

Nevermind that this is already official, now it's ULTRA OFFICIAL!

Thank god we had you here to tell us.

[kissing_toast]

Still L&P, there was coding for pets in Base Game if I remember correctly, the game just never used it.

[funnykid]

It's also official that EA is lazy.

[Robowolf]

It would be great (and fitting) if Pets came with plague and illness. I'd definitely play that expansion.

[immortelleMuse]

Well, there was coding for seasons found in Ambitions (possibly earlier, can't remember) with the fog emitter, and obviously the expansion after that included seasons... oh wait.

And if they brought back the guinea pig disease and made it actually deadly and contagious, that would be cool. Wouldn't count on it though.