The story contains the existence of alternate timelines but if they exist you can have as many timelines as you want and the story will never end. Winning the battle against Skynet would mean nothing because the characters can travel back in time and it can happen all over again, forever and ever.
Everything that happened in Terminator 1-5 will just be one of those timelines and anything can be changed at any time, including a win against Skynet if it ever happens. Also Terminator 1 didn't even need to happen if the Guardian could successfully protect Sarah Connor. Oh right, it's just an alternate timeline, so what's the point? Just create 20 or 30 timelines if you want the franchise to go on forever.
Everything that happened in Terminator 1-5 will just be one of those timelines and anything can be changed at any time, including a win against Skynet if it ever happens. Also Terminator 1 didn't even need to happen if the Guardian could successfully protect Sarah Connor. Oh right, it's just an alternate timeline, so what's the point? Just create 20 or 30 timelines if you want the franchise to go on forever.