This is great news!
There is a lot of very good documentation available on planning for capacity and availability planning for SharePoint Server. But Microsoft has not been idle. They have been working on a set of tools and models for SharePoint Capacity Planning, now in Beta. The tool can be downloaded from the Microsoft Connect site if you are a program participant. It allows you to explore the necessary infrastructure and hardware requirements based on projected usage.
This tool uses the System Center Capacity Planner 2007 (SCCP) as an engine to provide for data collection, visualization, simulation and report writing. The tool can be used in pre-sales and feasibility study of a deployment project to give you a rough estimate of hardware requirements.
Apply for participation in this program here: https://connect.microsoft.com/programdetails.aspx?ProgramDetailsID=1602