It's just a video game. It's $15 to $30 bucks (plus extra bucks for DLC characters) depending on where you get it from.
Fighting games IMO don't get outdated like sports games. There are people that still play original SF2 or Super Turbo but the player bases just get smaller with the times.
I suggest you buy it and try it for yourself. Don't wait on the new game, play what is available now.
Like learning any new skill, it takes time and experience for you to be well at it. Learning instrument, how to play a sport, etc. it will take time and experience. Plus, you have loads of resources around you to help you (this site, youtube, other sites that have good KOF information).
Any arcade stick for PS3 is good, (I use the SF4 TE fight stick), it all depends on how comfortable you feel.
Get it.