I did address these points in my answer actually, which I'll go into below... but first:
Clearly, FC have a plan to change stuff. Handing out a solid implementation date to players, even if that were desirable, won't affect when the implementation hits. The design and implementation stuff will take just as long, whether players know it or not.
People leave/stop paying for games when they don't enjoy playing any more. That's the basic truth.
Generally, if somebody is enjoying the game, they won't leave. If they're not enjoying playing the game then they'll tend to leave. As you say, there will also be whiners who complain a lot on forums, but when push comes to shove, they'll stay if they're actually enjoying playing the game.
Knowing a firm date, even if that were possible, isn't going to make the game any more enjoyable to play. Your MP is still going to be unwelcome in teams and unplayable in PvP, whether you know the date of some upcoming changes or not.
If they're not enjoying the game, then they may choose to just take a payment break... and then come back to the game when the changes hit. This group will largely take the break whether or not the changes are going to hit in January or June next year. Announcing a date won't really affect their decision... they'll go (or play freebie accounts) for now and come back whenever the changes actually hit.
There might be a very small group of players who will stick around if the implementation time is short enough, even though they're not enjoying playing the game. This is because they really want to continue playing but find that there's not enough enjoyment to put up with it. Most of them will return when the changes actually do hit, because they really want to keep playing.
Of your 3 groups:
1) People who don't care if the game's going to get better: well this probably really means people who are enjoying the game as it now is, really. They're happy to keep playing and won't leave... in fact they're all the more likely to stay because they see that the game is going to improve.
2) People who will get upset at every little thing: by which I think you mean people who tend to complain whatever's happening and won't leave anyway. The whine, but stay people.
3) People who want to know approximately how long they have to wait: There's little or no loss of player-base as a result of not having a deadline. There may be a period of slightly lower paying population during the development of the changes, which tends to come back again once the changes hit... but this is always true - and won't change whether or not it's known when the changes will be released.
Finally, I refer you back to my first post in this thread:
Earlier in the year, they said they wanted to get the rebalancing patch out for testing before the Graphics Engine release. At that time, they'd said that the graphics engine should be out around the end of this year. If you take those two things together, you could call it a very broad timeline of both Rebalance and Graphics engine out by the end of the year.
You said "All we're really looking for is confirmation that FC has a plan"... well there you go. Both statements there were directly from FC devs.
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