2 Added some additional thoughts.
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EDIT: After reading your comments above I had some more thoughts. It might help if you are able to take an agile approach to developing this app and break it up into different components that can each be fully completed before moving on to the next one. Your manager may be more likely to approve of you taking the extra time for new technology if he's able to see that you're making steady progress along the way. Also, you don't have to choose between writing the entire app in MVC and Entity Framework or ASPX pages and datasets. It's possible to use both in the same app using a hybrid approach. You could start out using MVC and entity framework for a few of the components. If things are going well and your boss is happy then you could continue, but if he feels that it's taking too much time you could develop the rest of the app with ASPX pages and datasets.

EDIT: After reading your comments above I had some more thoughts. It might help if you are able to take an agile approach to developing this app and break it up into different components that can each be fully completed before moving on to the next one. Your manager may be more likely to approve of you taking the extra time for new technology if he's able to see that you're making steady progress along the way. Also, you don't have to choose between writing the entire app in MVC and Entity Framework or ASPX pages and datasets. It's possible to use both in the same app using a hybrid approach. You could start out using MVC and entity framework for a few of the components. If things are going well and your boss is happy then you could continue, but if he feels that it's taking too much time you could develop the rest of the app with ASPX pages and datasets.

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Not becoming obsolete sounds like a pretty good business reason for using new technology. It flows both ways. You don't want your skill set to become outdated, but your boss should also be concerned that he might not be able to find employees willing or able to work on outdated technology. If the majority of developers and employers leave an old technology for a new one that might be reason enough for your company to do so too.

To specifically answer your question you should evaluate each one of those technologies individually to see if they meet your needs. I'll give you my take, but you really need to spend at least half a day to research and evaluate each one them as they apply to your specific business needs.

LINQ: This is something you can use, even without entity framework. LINQ is a technology used to work with collections of data, and you can use it in your applications even if you don't use it for loading that data from the database. Do yourself a favor and learn how to use lambda expressions and LINQ extension methods. It will save you time, make your life as a developer easier, and reduce the amount of code you need to write.

Entity Framework: This seems to be the future for data access in the Microsoft world. Most of the new frameworks, technologies, and tools from Microsoft are designed to work with entity framework. It's not perfect, but it's a lot nicer than using datasets, especially if you use LINQ to entities. One big business reason for using entity framework is that it reduces the amount of SQL code you need to write, as the framework will generate it for you. In my experience, most developers aren't very good at writing SQL anyway (and most companies don't have a dedicated DBA), so for most applications entity framework should make things faster and more efficient. Entity framework will also let you work with POCOs which have less overhead and are easier to work with than datasets.

MVC: This one might be hard to justify, as most applications might not benefit much from it. Based on the latest job postings I've seen, MVC is still in the minority (although it is gaining ground fast). For a most business applications MVC might be overkill, and dragging a few controls onto an aspx page will suffice. MVC has a learning curve to it, and to be productive and get the most out of it you really have to understand HTTP, HTML, CSS and JavaScript. MVC works well when you need to have a really customized web application where performance is a big priority. If that is not the case, and the employees don't have much experience with it, there probably isn't a strong business case for using it.

WCF Web Services: Do you have to provide data to remote client applications? WCF is probably the way to go. Are you just writing a web application that will run on the same server or local network as your database? Don't use WCF, you don't need it and it will only serve to complicate things with needless abstractions.

In short, use a new technology when it makes sense, and take the time to find out when that is. It takes a lot of time to learn new technologies, but it shouldn't take much time to evaluate them and learn if they will benefit your specific situation. This is something the higher ups in your company should already be doing, but if they aren't then you need to do it and then take the time to educate them on what you have learned.