People are saying (including WotC folks) SWSE and TBo9S are previews for 4E. People in this thread pointed to those products being play tested as evidence for play testing of 4E. These are essentially false claims as far as can be determined by public knowledge.
First consider how many of you have played a SWSE game with TBo9S?
How many with the clearly altered racial rules? (See the Elf preview)
How many have played SWSE with ToB9S and wizards with at will and per encounter abilities in addition to spells (which are often per day at low level now)?
How many people have used Resurrection as a Ritual?
I'm sorry neither SWSE or 3.5+Splatbooks is in no way a true play test for 4E, and to lead people to believe so is to mislead them. (When taken literally - which I haven't been, but it has been used so in this thread.)
To say that SWSE and the 3.5 splatbooks were used to test many ideas that 4E is based on is a different thing, and clearly (based on public knowledge) not misleading (and how I have interpreted the WotC Staff's statements on the matter).
Any significant change to a rule set requires significant play testing. That doesn't mean 4E needs a public play test, and without knowing what the numbers are of play testers its impossible to adequately critique the process WotC is following.
Yes I want to be on the PT team, because drat it I am well and truely done with 3.X, and 4E based on the ideas and concepts evident in SWSE, and many splat books such as TBo9S looks a lot more exciting to play.
Yes I also recognise that no amount of play testing is ever like exposure to the public at large. 500 people will always find more problems than 50 people. But effective play testing is more likely done with 50 than 500 initially because of signal to noise ratio.
Basically public play test is a disaster for WotC, and there is no legitimate way, without WotC knowledge, to claim more play testing is required.
But to claim the change from 3.XE to 4E is not significant, I think is also misleading in the grand scheme of things. Elves certainly changed as much between 3.5E and 4E as they did between 2E and 3E (based on public information).