Are Web Apps and Services Heading to Extinction?

Are Web apps and services heading to extinction? Mobile applications can embed common web functionality and interfaces--or--within commonly used apps, such as e-mail?

Specifically, web-based apps like Twitter have new competition in apps, which integrate micro-blogging directly into your e-mail.

Another example would be the many web-based calendar and event services. These independent web apps have their own interfaces.

Can a Google Calendar, Apple iCal, or Microsoft Outlook calendar dis-intermediate these web-based calendar services with the direct access they have to your calendar on mobile devices and your most critical calendar app?

Google, Apple, and Microsoft already have expansive and third-party calendars that you can subscribe to without going to any third-party web site.