As we had been warned previously, Innervate is being changed in patch 3.1.2 to restore a flat amount of mana. At the moment, it restores mana based on the spirit of the target. After the patch, it gives "450% of the casting Druid's base mana pool to the target over 20 seconds," which works out to a bit under 16,000 mana over the course of the effect.
So the effect of Innervate is no longer based on the target's spirit, or indeed any attribute of the target. Paladins won't laugh at you any more when you innervate them. It's also a big buff in PvP, since spirit is rare on PvP gear. On the down side, as many people have pointed out, this doesn't scale at all - it will always return the same amount of mana, no matter what the casting druid or the target is wearing. This is also a slight reduction from what a holy priest or a resto druid receives from Innervate right now, which is more along the lines of 20,000 mana.
Blizzard isn't too worried about the scaling issue; Ghostcrawler says "We don't think the lack of scaling at level 80 is going to be any kind of problem unless we introduced say 5 more tiers of content without also bumping the level cap. We aren't going to do that." And when we're all at level 90, the druid's base mana will be higher, so that should solve that problem.