pawsplay said:
Whether or not you are enthusiastic about 4e, I think it's pretty clear that a lot of 3.5 fans have understandable reasons to be annoyed with the new version, either because they weren't ready to upgrade or they aren't happy with the new direction. While AD&D 2e was languishing when 3e came out, 4e comes on the heels of a thriving 3e.
It is too some degree understandable, but is it warranted?
Many people say "I have so many products that could last me a lifetime". So basically these people don't actually need any more supplements - so why bother if no new supplements for 3E appear? Either they wouldn't have bought them anyway, or they would have wasted money!
Seen as an extreme, regardless of how much we have, we always hunger for more. And if we decide to hunger for 4E (so to speak), this means all the stuff we believe we would use will definitely be no longer used. Which means we really become aware that we wasted our money.
The other extreme, we wouldn't actually hunger for more products means that WotC has no choice but to switch to a different product and try to sell it. That's resulting in D&D 4.
That's only the business side of things.
On the other side, we also have the "creative" thing. The designers and developers of WotC are good at making rules. That's what they like to do. But how many new rules can they come up with, that will also fit into the existing rulework? At some point, the system becomes to complicated, to bloated, and to unwieldly. Balance becomes to complex to gauge, and the game will not work as nicely as it did.
And it's not only a problem for the designers. Think about the reactions to the new magical items in the MIC - many people object to them because they seem overpowered. They are thinking in the 3E core rulework and its assumptions, and products not following the details are not acceptable for them.
So, the designers and developers want a new system, because they just can't add something interesting and working to the new one.