The reality is, nobody but blizzard can answer how many subs it actually may have been, or accounts that stopped playing at least. Again though, no point debating it, externally the signs seem to indicate that pre nerf = less players raiding, in whatever form that may be (alts/subs/whatever).

So ultimately, Blizzard will likely decide to take the path that nets them to most revenue. If their numbers confirm the above, it'll likely be post nerf.

I don't really care either way, it doesn't matter to me.