Previously Microsoft had released the Beta 1 and  2 versions of Visual Studio 2010 and .Net framework 4, news is that RTM version would be released by March 22nd 2010.This has been delayed coz of some performance and some virtual memory issues.Beta 2 was focused on performance and stability, including integrated tool for SharePoint, including project templates and debugging support, and support for developing Windows 7 applications.

Visual Studio 2010 and .NET Framework 4 Beta period has been extended and another release (RC) will take place between the Beta 2 and RTM in February 2010.

ScottGu quotes

We’ve also received feedback that the performance and virtual memory usage of VS 2010 Beta 2 is not where people need it to be before we ship.

We’ve been doing an intensive performance optimization push the last two months that is delivering significant performance and virtual memory usage improvements across the product.  The early feedback from a small set of customers testing interim builds since Beta2 has been positive about these improvements. We still have several big performance fixes in the process of being checked in that will improve things even further.

In order to ensure that we are able to receive and react to this feedback, we will also be moving the launch of Visual Studio 2010 and .NET 4 back a few weeks.

Until then download the Beta 2 of Visual Studio 2010 for different versions

Visual Studio 2010 Ultimate

Visual Studio 2010 Premium

Visual Studio 2010 Professional

Visual Studio 2010 Express