And I'm just wondering whether we can meet the next-generation of Apple watch, maybe series 5 or 6, which allow us to use it as a mobile hotspot in the future?
Apple Watch Series 3, null
Correct. The Series 3 GPS+Cellular Apple Watch uses the number / line from the paired iPhone.
Your carrier may assign the watch a number that is different to the one on the iPhone, but that number is for billing purposes only, and cannot be used to receive calls or messages.
The Apple Watch receives messages and calls to the number from the paired iPhone only.
Unknown, since there is no series 5 or 6, and Apple has said nothing about them, there is no way for anyone to know what if anything they may be able to do.
You can provide Apple Feedback about what you would like to see available on the next generations of Apple watch by filling and submitting the form here: Feedback - Apple Watch - Apple
Excuse me, so it isn't available for us to use the different phone number on our apple watches right?
Can I use another phone number, which is supported by the same telephone operating company as my iPhone use, on my Apple Watch 3?
