Kill Team Scouts Questions Loadout/Longevity

So a few things. I am newish, as of April, have a huge army but don't have Scouts for my Ultramarines. There seems to be some tumultuous things around the Kill Team Box Sets, one being they're already planned for obsolescence in Kill Team and getting new boxes that will cost more soon. However, from what I can see, they were only released in the past 9 months as new sculpts. What's everyone's opinion on their longevity in the 40k universe? I don't play Kill Team (but might at some point), however, I primarily want them for my 40k army, but don't want something that may go to "Legends" in a few years.

On top of that, what is the optimal loadout for Scouts for a 40k Army?

Thank you in advance.