A nerf in LoL terms generally is pretty light and I doubt they can nerf the distance that much. I can see them adding CD and I also think its much needed.
The benefit Flash provides is just too good in general, just think about it. Instantly changing positions is a huge advantage and people will still need it to jump walls, initiate team fights, set up kills. It probably won't be nearly as prominent, but I still think it'll be one of the main spells everyone will take for quite some time. Promote seems limited to pushing, Surge IMO will probably be a 1 per team type deal since team fights generally don't last that long.
Flash will still be a staple for positioning for many champions seems positioning in any game or sport is just that crucial regardless. Ghost doesn't allow you that type of benefit, freedom or flexibility that even a slightly shorter Flash on a longer cooldown will provide. Plus this places more value in more people considering utility tree over the other tree due to its mastery.