I think they've recently decided that promoting .NET for its own sake, or even making money on dev tools, isn't a particularly strong goal of theirs and the tools business should have a primarily subordinate role supporting their platforms (Windows, Windows Server / Azure, Windows Phone). You can see this in their recent org chart changes (whereby not only is Scott Guthrie no longer VP of the .NET Platform, but there is no longer a unified .NET Platform team at all - instead, each part of the framework has now been moved to the org tree of some product it supports. WPF is part of Windows, ASP.NET is part of Azure, Silverlight is part of Windows Phone, the core CLR is part of Visual Studio, etc.) or even in the recent redesign of the MSDN front page (where "Platforms" are now front and center).

This doesn't mean Microsoft is somehow out to kill or abandon .NET as I've seen some panicked .NET developers speculate recently, but it does mean they want .NET to be firmly in support of their platforms and not the other way around, and if there's a choice between doing something that will help .NET and something that will help Windows et al., they'll take the latter.

In terms of "openness vs. lock-in" this is probably a lateral move - they're more open to Windows et al. being less locked into their tools (or their tools' revenue streams - e.g. the tools for Windows Phone and Win8 Metro style apps are a free download), but less open to their tools being less locked into Windows et al. (e.g. cross-platform Silverlight), or even the latest version of Windows (e.g. .NET 4.5 is Win7/8-only).