Gyarados is already really good as a generalist attacker, and Gengar is pretty solid if you can dodge effectively. Jolteon and Flareon already received a pretty significant buff in the CP update, as Flareon is one of the most effective Lapras counters and Jolteon is important because every baddie puts Gyarados in gyms now.
Rhydon got a huge buff, and Golem doesn't need a buff because he's basically Rhydon-lite.
I'm not sure we need to see more Gen1 pokemon getting a buff, but I could see Niantic making some changes to the CP formula to shake up the gym situation. I am sick of seeing mostly Gyarados and Rhydon in gyms, as these pokemon are terrible defenders.