But the flip side is most of them tell you ahead of time whether something is recommended for new designs, and how long they will guarantee production for.
Which is much more important.
In this day and age with FPGA companies being merged and spun out left and right, i doubt anyone relies on the future line announcements this second.
In more normal times I agree you want to know if you are going down a dead end path.
Having knowledge of upcoming parts is important in hardware engineering for planning purposes.
And you can very often prototype with either an overpowered development board or you own prototype board with another FPGA, and then downsize appropriately as the project advances. Most importantly, if you know there will be a viable version in a year, you can postpone the final decision and Xilinx get to avoid having you choosing Altera now if it's possible that their new offering will match your project.