If there's a possibility that Taeyeon and Wendy would leave SM then they basically would've lost almost ALL of their main vocalists from Gen 2-3 (individual contract wise)

It's clear that Taeyeon has openly announce her dissatisfaction with SM regarding SMTown and Wendy is mysteriously absent for "personal reasons". I hope all goes well for them behind the scenes, but if contract fiasco happens and they all ended up leaving... then SM would create history of having ALL of their Gen 2-3 groups losing their main vocalists, either by left the group completely or have their individual contracts not resigned anymore.

Let's start off with TVXQ, with their main vocalists being Jaejoong and Junsu, which I probably don't need an introduction on how they left, sorry, SUE the company for their inhumane contract. Super Junior still has Ryeowook and Yesung in their company, but Kyuhyun who is pretty much the best male idol vocalist of all time left them in 2023. SNSD infamously lost Jessica, their main vocalist in 2014, then one by one, Sooyoung, Seohyun, and Tiffany left in 2017 followed by Sunny in 2023. If Taeyeon left then it means the ENTIRE SNSD vocal line would have left and renewed the contract with SM. Finally Shinee who sadly had Jonghyun pass in 2017, would also be left by their other main vocalist Onew and their lead vocalist Taemin in 2024. And this still have yet to count the groups that are no longer active like The Grace that has Lina and f(x) that has Luna in their lineup.

Coming up to third gen, EXO has a powerful main vocal trio of Baekhyun, Chen, and D.O. D.O. left and made his own company in 2023, followed by Baekhyun and Chen alongside Xiumin who left in 2024 and to say their legal issues with the agency are getting messy is an understatement. NCT of course had Taeil absolutely well deserved to be kicked out and not the fault of the agency, and also pretty much at least for now the rest of the other main vocalists are still standing. But Red Velvet would be the kicker, because if Wendy truly is not renewing her contract, of course purely going by the ongoing speculations on why the hell did she disappeared on last SMTown and the album making as well, this would mark a history for SM themselves of basically losing their entire main vocalists from their groups in one way or another.

You look at the list on a lot of their artists who have left even in the last two years basically just make you go oh my god they fumbled hard. So many talented artists on their disposal and they almost can't seem to ever keep their talents that a lot of agencies would dream to have. I root for the rest of the artists to get their well deserved better treatments or if not, for them to not renew their contracts any longer with that agency.