Is Seam an template type framework where we can configure any, each of the MVC technologies with Java?
I'm not sure what you mean by "template type framework", but Seam is an integration framework that gives you choice in your presentation layer. Support is continually being added in this area and Seam 2.1 now supports Wicket.
Seam is too easy, to get the basics.
Well, I would say that's a good thing

But, yes, as with any other technology as you get deeper into development with Seam, you will need to understand more about the framework and its underlying technologies.
How and what way Seam intercept persistance/model? Hibernate/JPA/any other?
Seam allows you to scope a managed persistence context to a conversation (often referred to as a web transaction). This avoids the nasty issues associated with detached entities such as LazyInitializationExceptions, constant merging, etc. It also provides the first layer of caching in your application as the persistence context holds all of the entities that have been loaded through the course of the conversation and simply references those in-memory instances when requested. That way you are not continually going back to the database to fetch entities as with many stateless architectures.
Any simplicity towards enhancement of the Seam Framework, from developer's perspective?
I'm assuming you are referring to extension points of the framework? Seam provides great flexibility in the way you develop your application. You are not tied into any one particular approach which was one of the goals of the framework.
Speaking from experience, I have developed a number of complex enterprise applications with Seam and have yet to come across a situation that I could not handle by either taking a different approach, or extending the functionality of Seam in some meaningful way.
To what extend/depth Seams can be integrated with Springs (yet to look into it) ?
Seam supports direction integration with Spring. See:
http://docs.jboss.com/seam/2.1.1.GA/reference/en-US/html_single/#spring for the details.