Today Microsoft announced Visual Studio 2015 and .Net 2015, which normally wouldn't be incredibly exciting except the announcement also included details on how the .Net compilers are being made open source and ported to Mac and Linux platforms.
There have been community projects for years to allow .Net applications to run on non-Windows platforms, but to have an officially-supported cross-platform resource is huge. Microsoft has slowly been nibbling away at the marketshare of LAMP (Linux/Apache/MySQL/PHP) environments for years, but the single greatest barrier preventing most smaller shops (which make up the vast majority of web developers) from buying into the .Net ecosystem has been the infrastructure to support it.
Traditionally, .Net applications have been run on instances of Microsoft's Web Server, IIS, which is installed on Windows Server and is usually supported by a MSSQL back-end also sitting on top of a Windows box. The licensing alone to get this kind of setup can easily push $1,000 and doesn't even include basic things such as a development environment or a source-control platform.
LAMP environments, however, generally involve $0 in licensing because the majority of the components have been placed under the GNU General Public License. This makes it super easy for any 4th grader with a access to Google to learn how to start developing apps in a LAMP environment (often with disastrous results, but that's another topic for another day).
Whether or not the availability of IDEs or the affordability of the infrastructure has had anything to do with it, there's probably a greater demand for LAMP servers than IIS servers in the personal/light commercial sector because most COTS (Commercial Off-The-Shelf) Software is PHP-based (That's the "P" in LAMP). Wordpress, Joomla, Magento, and even Facebook are written in PHP (Yes - Facebook uses a heavily modified version of PHP, but it's still PHP). You can run Apache on a Windows box - but why would you (or your hosting provider) pay $700 for a Windows Server license when you can slap it on CentOS for free?
With it now being somewhat easier to get your nose into .Net development, hopefully we'll start to see more mainstream applications written in .Net.
I've always personally preferred Linux over Windows hosting because in my experience Linux servers have generally been more stable than their Windows brothers and sisters. Part of this may be due to the fact that I've always administrated minimalist installs of Linux boxes whereas 90% of the Windows boxes I've touched were running something over than Windows Server Core, which in my opinion creates unnecessary overhead and more vectors for stuff to go wrong. I'm sure there's a left-click-island-adventure sys admin out there somewhere who would love to debate me on that, but that's my story and I'm sticking to it.
If it isn't blatantly obvious, I'm completely stoked about being able to run .Net apps on Linux now without the 'community-made-module' cloud following me around everywhere.
Fanaticism aside, I said all this being said to make this prediction: With .Net being officially ported to Linux, organizations small and large alike may very well see real cost savings by phasing out unnecessary Windows boxes and even taking a second look at the performance benefits of MySQL vs MSSQL for application hosting and back-ends.