Unless I am misreading the functionality of DAZ|Studio, DAZ is going to provide the functionality of Poser 4 for free.  Advanced functionality, like plugins to other applications, will be for sale.  Below is a list of features [Source: DAZ], and the current schedule:

Items included in the initial stage of the DAZ|Studio Beta Program:

• Support for Windows 98SE/2000/Me/XP and MAC OSX 10.2 and above
• Single select and edit of bones or objects in scene via controls in the Scene pane (i.e. visibility, color, and position)
• Cameras, props, scenes, and figures can be posed and manipulated using controls in the Parameter pane
• Material editing will allow user to alter properties of existing materials
• Editable material properties include: surface color, surface texture, bump map, transparency map, and displacement map
• Open-GL support in 3D views including: real-time texture and transparency maps
• Import of .OBJ and .PZ3 (including all PZ3 subsets) file formats.
• 3Delight renderer by DNASoft included (Renderman compliant)

Items that will be implemented at a later stage of the DAZ|Studio Beta Program:

• 3D view display will be optimized for speed and quality
• Save function enabled
• DAZ|Studio specific file format
• Selection of objects through 3D view
• Additional Open-GL support in 3D views of: anti-aliasing, depth of field, and specularity.
• Animation timeline that allows user to set and edit keyframes, create, and play animations
• Python support
• Advanced asset manager for handling large asset quantity and content directories
• For-sale plugins for .LWO and .MAX import/export

Anticipated Stages of program completion:

• Limited alpha (current stage)
• Initial Public beta release
• 2nd beta release, Lightwave 3D® and 3ds max® Plug-ins available
• DAZ|Studio Basic 1.0 release
• Gradual addition of plug-ins with advanced features

[Schedule subject to change]

Does it have the functionality of the face, hair or cloth rooms in Poser 5, no.  But, if you are a DAZ customer and purchase their products, do you really use the previously mentioned rooms much?  Will they provide similar functionality?  Who knows.  Maybe Dan Farr and Chris Creek do. :)