NezziR answered pretty well, but I'll add mine too.
FFG did not tell anyone that they were making a new game
It was a Marketing strategy to shorten the time between the excitement of unveiling and release, to try to capitalize on the initial buzz about the game and prevent the excitement from petering out (which can happen with a long time before release). This is completely valid and reasonable strategy (even if, in this case, it didn't necessarily work as well as they hoped. They underestimated the reaction of a vocal portion of their fan base).
FFG did not ask the existing fans for ideas for the new edition.
How do you know? Perhaps they did not create an open forum for it, but perhaps they did some various polling. Or perhaps they just lurked various boards and picked ideas up on what to fix or implement. Or perhaps they had a private mailing list? Some of them are WFRPv2 fans, so they provided input too.
FFG have not conducted any playtesting outside of their own employees.
Again, how do you know? Any playtesters are probably under an NDA to not say anything about it until release. You have no idea how many playtesters they used, and how many of those played WFRP v2.
FFG have chosen to completely change the system.
Yes, they are *mostly* changing the system. (You can't say completely, because they kept many of the stats, the careers and career system, etc). It has already been stated they are trying to bring in new people into the game. As I pointed out, if they made v3 as an update to v2, what new players would they gain? Anyone not-interested in v2 wouldn't buy it, and anyone interested interested in v2 would have already bought v2 (and therefore not a 'new' player). So, they change the game to make it different enough from v2 to entice new players to try the new version of the game. This has nothing to do with them hating the v2 players, or not caring about v2 players. They hope the v2 players will try and like v3. I'll quote back to you:
Are you really insane enough to argue that FFG doesn't want any v2 players to play v3?
You only have to look at the reaction from the majority of the existing fans to realise that this game was not aimed at them at all.
Umm.. what majority? Looks pretty even to me, for and against, on these boards. Your statement here is obviously incorrect and false. There is no "reaction from the majority of existing fans..." and patently no substance supporting your conclusion. I agree, v3 is more focused on trying to get new players into WFRP, than appeasing v2 players that wanted v3 to be an upgrade of v2. I'll even suggest it's possible FFG is more concerned about getting new players, than losing v2 players that don't like v3. Neither of those means, however, that they have no regard or desire to try to keep as many v2 players as possible (while also adding new players to the fan base).