I wasn't aware there was any intent to have apps migrate en masse to XCB (does anyone know of
anything other than Xlib that uses XCB yet?). What is more likely to be useful is to have
*widget sets* migrate, as they already implement most of what Xlib does themselves, and don't
need most of the rest except for the raw comms stuff which XCB provides.
As far as I know the XCB-based Xlib is here to stay.