Is getting an iPhone 6s Plus today(2017) worth it than getting the new iPhone 8 or iPhone X?

I currently have an iPhone 6s, I love this phone it works great and I don't think there's anything wrong with it, but the only reason I want to switch is because I got it with only when I bought it, I thought it would be enough but it wasn't. I don't really want the 8 or the X cause they don't really interest me, the only reason I'm considering them is because they are newer phones, so they are built with newer, better equipment (processors and stuff like that), so that means that the 6 is now outdated. So If i do get the 6s plus, will I regret it?

Well no, for the reasons you stated. Not to say the 6s Plus is a bad phone but just not the best iPhone available now. A change from the 6s to the 6s Plus wouldn't be much of an upgrade. So I'd suggest at least a 7 Plus if possible.

Oh & as far as the 6 being outdated, no. It is still being updated & would be for at least 2 years.

The 6 and 6s are still far from being outdated.

My three year old iPhone 6 128GB still runs all current apps perfectly well. Other than a few gimmicks, the only really useful gain on later models such as the 7, 8 and X is the water resistance. But as I've never had a wet phone in the twenty-six years I've been using mobile phones even that feature is of little genuine use to me.

So if the only thing wrong with your 6 is the paltry 16GB, then trade it in at a shop such as CEX to buy another 6 or 6s with the maximum 128GB option. Or maybe a 7 if you want it to look like you may have an 8 as they look almost identical (hardly surprising, as the 8 any other year would have been called a 7s). That will save you a fortune on the cost of upgrading and CEX guarantees everything they sell for two years.

Not only does that save you money, but it gets you time to allow Apple to sort out the many faults the X has, such as poor facial recognition and faulty OLED displays. Wait for the Xs?