Just my two-penneth...
This sort of thing is possible with 1.5.0svn by using markers but I've no idea if this functionality will be available in the final product.
To create a marker, put the caret in the text where you want to get the page number from and choose menu "Insert -> Marks -> Anchor Mark", give the marker a name and OK the dialog.
Then, in the text where you want the referenced page number to be, put the caret in the text where you want to put the page number and choose menu "Insert -> Marks -> Reference to Mark", choose the named marker and OK the dialog.
It seems to work okay but be warned that 1.5.0svn is not for production use at the moment. And files created with 1.5.0svn cannot be loaded back into earlier versions.
If you want to use this feature I'd recommend saving a copy of the document in 1.4.? (with a -dev suffix in the file name, or whatever) and loading this copy into 1.5.0svn and trying it out there so you don't lose the original. (You might want to wait until the very end of your workflow before using it properly.)
Tester beware! If in any doubt, don't risk it.