If you want to have influence in what direction Nagios is going, you have the chance now.
Ethan Galstad, the founder of Nagios has done a great job to open up the project and listening to input from the community.
Go to http://ideas.nagios.org/ and vote or add the functionality you want in Nagios so others can vote for it.
I have added the idea that Nagios should have a programable rule engine. When I worked as a Tivoli consultant it was essential to collect information from different sources and write som rules and present the result. All the enterprise monitoring solutions has a rule engine, i.e PEM (Patrol Enterprise Manager), T/EC (Tivoli Enterprise Console) and so on.