Ultimately does it really matter? WordPress the software is open source GPL and even if Automattic is acquired, Matt will continue at the helm of the WordPress Foundation which is a separate organization.

@Carl Hancock - While this is very much true, selling Automattic and WordPress.com would have an impact on the open source part of WordPress too.

Don't forget that lots of the code that is committed to the WordPress core, finds it's way to there via a real life test at WordPress.com. WordPress.com is a huge group of users who are automatically testing new features, without even knowing it. Only bugs will be reported.