The answer is likely no because neither does WOTC.
I'd rephrase that to, "The answer is likely no because WOTC doesn't want to preview material that is still under playtesting and might be revised. They don't want to do that because certain persons will jump on any errors in it and proclaim doom and gloom across the internets."
If I were looking a previews for a car I would want to know it comes with a 2.5L V-6, not that it drives "ultrafast".
And if you were being billed today for material that won't be released until February, you might have a really good point. But that's not the case, and you don't. If you don't feel the current previews provide you with adequate information with which to judge the quality of 4th Edition Dungeons and Dragons, feel free to wait, and make a purchasing decision only when your needs have been satisfied.