When Microsoft bought FoxPro, leading database app of the day, in 1992, I remember, an intriguing question among programming community and geeks was whether MS will use the Watcom compiler, which was used for building FoxPro to that day, a compiler which was state of art at the time and better, or, use their own inferior MS compiler to build the next version of FoxPro… I never followed-up, and don't know the answer, still the question remains as a fundamental one. (FoxPro was later renamed as Visual FoxPro and died in 2007 at version 9).
A platform needs to be taken seriously. For quite some time Flash (whatever you meant by it) was seen as a toy for creating animations for the web, including the ones that made you look for the 'skip into' link and really annoying advertisements that hid content. Most of the time this was true.
Things improved in time, but it's always hard to change initial perceptions.
I'm now skipping pages of info that may bring the reader up to date with Flash history, for the sake of coming to my point.
I may be seeing what is not there… But I see the Flash Platform as the main platform of the future: OS-wise cross-platform, on both desktop and web, and on other devices… "Flash Platform" is not "Flash" (whatever you understand by it). You can't consider something as a platform just because you can write RIAs for it or it has a desktop component, or just because you have a few different editions. It's bigger than that. It has to be…
Java started with the promise of making apps that you write once and run everywhere. As I see it, it failed to achieve this. I see Flash replacing Java, achieving this initial goal. I see Java (not JavaFX) as a rival to Flash as a platform…
The developer types who were expected to jump into Flash train with Flex were mainly Java developers, as Java is also a scripting language, just like actionscript.
How do you convince a Java developer that Flash (platform) is better? Will you have any answer when he reminds you that 'recommended professional developer tool', now named 'Flash Builder', is just a plug-in for Eclipse , which is build primarily in Java? Will you have an answer when he mentions that the AS3 compiler is also build in Java?
If I were a Java developer, at best I'd say Flash might be better for 'animation and stuff' only. If Flash Platform relies on Java, then it's inferior to Java, as a platform, no need for further discussion.
I don't think embracing Java is an option for Flash Platform. Flash will be the platform of choice and the better one, or it will be a toy animation platform (with some scripting capability). I don't consider being open source or not coming from MS as valid reasons for embracing Java. Also I cannot picture a stable co-existence, with similar usage ratios, being 'second best' is not an option I will be content with.
With AS3 and JIT, as I had written before, I was hoping the AS3 compiler would be in AS3… AFAIK, this has not happened yet. For this reason, professionally as a programmer, I don't consider actionscript as mature. If actionscript is a serious language (even though it's a scripting language), it has to have a compiler written in actionscript (this is my idea for maturity, you are welcome to disagree).
As I see it, for success, Flash Platform should get rid of any reliance on rival platforms (Java, .Net etc.) as soon as possible. (3rd party tools are OK, after all, they are additional tools. I think a platform should provide at least basic building tools, sufficiently advanced, that does not rely on rival platforms. [As soon as possible may mean years - but I believe this should be the agreed goal]).
Silverlight is not a rival to Flash Platform, .Net is. Silverlight is the toy animation  part of (web part of) .Net Platform. I believe Flash, as a platform, should have bigger goals than beating that.
People ridiculed Microsoft, when they used Flash rather than SilverLight for promoting some stuff. I'm surprised I'm not seeing anyone mentioning Java use with Flash. Is Java a better programming platform, and Flash Platform is really only a sub-platform for animation (and maybe minor RIA stuff)? Is this the planned and expected future role for the Flash Platform?
Is it because it's so obvious that Flash will ditch Java use when the time comes, that nobody mentions it? or are my expectations for the Flash Platform unrealistically high? I wonder.
I can write more, but I think I made my point.
Watcom C compiler went to Open Source heaven in 2000. Borland C++, which was considered better than Microsoft Visual C++ compiler (MSVC) by many in its time, died even before Watcom. Whatever route MS took then, when building next FoxPro version in 1992 doesn't really matter now. Today, MSVC is alive as it can be at version 10 (as preview, to be released)…
(And I now think blogging more is sure to make me unpopular, so I will stop).
 I don't mean to show disrespect to "Flex Builder" developers (both actual developers and people using it). Sorry if I sounded rude, it was to make my point clear. I think "Flex Builder" should be a native or Flash application, in principle. I don't 'demand' it to be done 'now', but I believe this is something everybody involved should know and agree and expect as a realistic future goal: A better IDE than Eclipse in every way, written in actionscript, running way better than any Java app can run, in Flash VM… (Same applies for the AS compiler).
 Obviously SilverLight (or Flash) is more than just a 'toy for animation'. The usage is for making my point, hopefully, more clear.