Sorry, no. We have not control over the resultant prefixes in the output. This kind of reshuffling happened to me a couple of times too.
What you can do is add your Assembly to the custom extension xml where you can set your own namespace, which you'd then use in the inline Xsl. The Map compiler will not alter that.
Custom Extension: http://msdn.microsoft.com/en-us/library/aa547368.aspx
Unfortunately, there is a bug in Visual Studio that prevents that value form being saved. Here's the workaround which does work fine: http://gallery.technet.microsoft.com/scriptcenter/BizTalk-Mapper-Custom-3050cb3e
For similar reasons, I always use the full namespace on nodes generated in inline Xsl also.