I don't think Johns is in love (so to speak) with Supes/WW. It's almost certainly not his idea. He wrote Lois/Clark very well in his various Superman runs and he's the one (along with his mentor, Richard Donner) who actually gave them a kid! The whole Superman/WW thing seems to be coming from Didio and Lee. Johns is a pro - even as he was trying (along with Mark Waid) to talk Didio out of killing Nightwing off in Infinite Crisis he was completely prepared to do it if Didio didn't relent. Likewise, he was the one who killed off Superboy who is probably his favorite character. Johns will do the job (even if he is COO) but it seems (IMO) he's not a huge fan of it.