Customers asking to upgrade a product from 1.1 to 2.0 raise this question. I cannot find any dates on microsoft.com. Perhaps one of you chaps know.
Probably not for at least another 6-8 years. Think of how long NT Server lasted.
Also, there is no .Net Compact Framework 1.1, only 1.0 (which was released with regular Framework 1.1, there was no CF release for .Net 1.0) and now 2.0.
Search results from support.microsoft.com:
.NET Framework 1.0: Mainstream support ends 30/06/2007, extended support ends 30/06/2009.
.NET Framework 1.1: 30/09/2008 and 30/09/2010 respectively. Since .NET 1.1 is a component of Windows Server 2003, extended support for .NET 1.1 on Server 2003 will run out when the OS does, currently 30/06/2013.
I can't see any statistics for .NET Compact Framework 1.0. I would hope that it will be the same as for .NET Framework 1.1 since they both shipped with VS.NET 2003. Right now VS.NET 2003 is showing 30/09/2008 and 30/09/2013.
There's really no hurry unless you want to take advantage of new features.