Silverlight currently supports Internet Explorer, Firefox, and Safari, Windows and Mac OS, but no Opera or Linux. Still, I have to say, that’s definitely progress for Microsoft. On the other hand, they don’t exactly have a choice if they want mass adoption. Flash is definitely a cross-browser as well as a cross-platform plugin, and it has been thus so for quite some time. I have yet to hear anything in terms of Opera support, but there has been news of Linux progress made for Silverlight. Unfortunately, by progress I mean discussions but no public builds. Of course, that’s irrelevant when it comes to IE8, but it’s only fair to give a good background overview.
Microsoft is already testing websites with Silverlight-only features, and version 1.0 was released over three months ago. Internet Explorer 8 has not even reached beta form - there is plenty of time to get a new version of Silverlight finalized (1.1 has been in alpha form since September as well). One thing is certain: Microsoft has not picked an easy road for itself. Macromedia (now part of Adobe) has held the crown for ages. If you want multimedia applications on your website, there really isn’t a solid alternative to Flash. Consequently, Flash has not had many major changes over the years, although Adobe has recently made one big improvement: Adobe Integrated Runtime (AIR). It should be noted that Sun’s JavaFX also wants in on the fun, but that doesn’t seem to be making as big of a splash as Silverlight, although if someone believes otherwise I’d be interested to hear their perspective.
AIR, previously codenamed Apollo, is actually meant for building rich Internet applications and exporting them to the flash format (.swf) or HTML files. Ideally, it is meant to ultimately succeed Flash, but in reality it is just a cross-OS extension to Adobe’s Flex Software Development Kit. AIR does not have an Integrated Development Environment: developers are encouraged to use their existing web development skills in HTML, AJAX, Flash and Flex. The point is, it isn’t exactly a successor to Flash, so it’s not as if Silverlight will become obsolete before it can reach a solid adoption level. As we’ve seen with Firefox and IE7, competition can be a wonderful thing. Chances are (given Microsoft's reach as well as IE's market share) that in a year or two, it will be necessary to have both Flash and Silverlight installed to get the “full online experience.”
Returning to the original question though, I honestly believe it comes down to whether or not Microsoft deems Silverlight ready to go. I personally haven’t seen any major quirks (or minor bugs for that matter) with version 1.0 (except for the lack of a x64 version, which Adobe happily doesn't support either), but then again there aren’t that many sites that make use of the wonderful technology. Microsoft can’t afford to push an unfinished version of Silverlight. Well, actually they can, but it would be such a waste seeing as the demos so far have been very impressive. If Microsoft does indeed plan to bundle it, I wonder if they will bother putting a checkbox at the beginning of the installation of IE8. If so, will it be checked by default? Anti-competitiveness is something Microsoft will be sure to try to avoid.
If you can’t see Microsoft bundling Silverlight with some version of Internet Explorer, how do you believe the software giant will push its Flash killer? Darn, I said it.