I can't seem to find the post now, but whoever claimed there was no backward compatibility of 2E to 1E, was absolutely wrong.
I started playing the Red Basic set and AD&D 1E around the same time, in 1984 or so (I'm now 35). When 2E came out, our regular group adopted it right away. One of the big drawcards for us was it's back compatibility with AD&D 1E.
Our 2E game often included a lot of 1E crunch, and we would often run 1E modules with 2E characters. Converting something from 1E to 2E, or vice versa, was a simple and intuitive process that rarely took more than a few minutes.
When our group resumed after a hiatus, there was a lot of debating about whether we should stick with 2E or move to the current set (3.5). Of our group of 5, 3 were 1E/2E veterans, 1 had only played a smattering of 2E but mostly 3E, and 1 was new to D&D altogether.
So we bit the bullet, and went to 3.5. After a lot of initial skepticism, we all eventually grew to like 3.5 (although various DMs still used houserules for a more 1E/2E feel). The major stumbling block for me, was trying to resume my established 2E campaign world, as the various crunch changes made it difficult to easily port over to 3.5. But I got there eventually, and was glad after I did.
I can assure everyone here, I won't be repeating the process with porting it to 4E. WotC have made it abundantly clear that there will no real guidelines to conversion, nor the system designed with ease of conversion in mind. The fluff is also getting so drastically altered it will seriously impinge on the tone (and even crunch) of my homebrew.
I can live with that - but it does mean that my primary group won't be contributing any finances to the future of D&D through any 4E products. If that's an example of a "grognard" killing D&D, then guilty as charged, I suppose. My disposable cash flow will go into supplements and adventures pitched at 3.5 gamers by various publishers. Does this mean I want to see 4E fail, or am telling people not to buy it? Not at all...
Also, add me to the group that doesn't buy into the fact that 4E will net a significant number of new gamers. Various other systems who have upgraded editions over the years have failed to woo me with promises of a relaunch. If I wasn't interested in Yakmaster 3E, Yakmaster 4E Colossal Editon (now with more Yaks) is hardly likely to win me over. Neither, I suspect, is it any more likely to draw in new P&P RPGers.
Couple this with the withdrawal of hard copy monthly periodicals, and the inferred reliance on a web based subsciption to keep up with the latest ed, and I suspect the "future of D&D" is on shaky ground. As many others before me have said, there is nothing wrong with looking for ways to rope in new gamers, but to do it at the risk of alienating hardcore fans with disposable income is bordering on commerical suicide.