There is a variaty of changes happening.
-100 plus pages of errata
-new directions in some later books (MMIII is the prime example)
-the essentials, compatible but basically a redo on both player and monster side.
-?
The "?" is what happens post essentials. Are getting "expert" rules to go with the "basic" ones?
Besides confirming that this is quite a bit of change, not really sure what to think (well besides that statement in my sig). We will learn more from Gencon, the DDI previews, and of course when we start to see this stuff.
Yes, but there's a huge difference: they're not trying to sell you a reprint of the same old stuff.
The reason 3.5 irked a lot of people is that most felt they had to buy the same set of books twice. Once you bought 3.5, your 3.0 books were pretty much useless.
Essentials doesn't work this way: if you buy the Red Box, for example, you're going to have a couple new builds per class, new options for the old races as well as new feats and powers.
Sure, there's some overlap with the first PHB ( the races, for example, some feats, the combat and skills chapters...) but you're also buying a lot of new material.
In addition, the errata includes a crapton of powers, feats, PP features and class features that aren't going to be reprinted neither in the Red Box nor, probably, in the rules compendium.
Finally, if you play an "essential only" game, you're going to lose any previously released class builds, feats, PPs and EDs, while when 3.5 hit the street, you could just sell your old Core books and use the new ones.
So I still don't see this as a 4.5, not even close...