I'm so disappointed the sims is potentially ending next year,

The person you're referring to is of course Pixelade, who is more of a critic of The Sims than anything else these days - he's spreading a very negative view of the game. I liked what he said before, but not anymore. And without saying any more, everyone knows why. It's his livelihood that's at stake. Even today, he can't let The Sims 4 alone...

Exactly, couldn't agree more! - Pre-teen stages are nothing else than a childish thing to demand, wouldn't be surprised if that mostly was "pre-teens" themselves who wish that. Who want's your sims to be stuck in that kind of stage, when the normal thing in Sims is to became a teenager, youth, then an adult and at last an elder? And even after that, there are many other alternatives.

Colorwheels was the worst thing in Sims 3, I would not like to have it back in Sims 4! Took too much CPU, and it took me forever to change certain colors and can't say anything else than that was terrible.

I'm happy about that because game cant take more dlcs or big updates, starting fresh could be nice with open neighbourhood colorwheels etc.

There is posts from a well known…for want of a better word insider, who indicated that the last Expansion pack will deal with Royalty, Medieval themes etc. This person is generally accurate and a trusted source. This will come next year and everything else that follows will be some kit or another. 

There's a rumor going around that Sims 4 is ending in 2026 and a newer version is coming also I can see that for short players Sims who play like that but as for myself I see Preteens as another Lifestage like infants and toddlers were added. Just like what's the difference between a YA and an Adult besides the Adult looking slightly older? 

What makes you think Sims 4 will end next year?
A pre-teen stage would only last a couple days so not really worth it. Height sliders are problematic though I hear that there are mods for this that mostly work.