Indeed, this has been on our long-term plans for awhile: github.com/CellProfiler/CellProfiler/issues/71
I can't estimate when this will be done though, but your input is noted!
In the meantime, a workaround could be to use ExportToDatabase, via either these two options:
(1) In ExportToDatabase, use the MySQL/CSV option. You don't need to have a MySQL server here. The per_image and per_object CSVs should be exactly(?) the same as the ExportToSpreadsheet output except that there will be no headers in the file. The headers are in the *.SQL file which you can read off in the same order as your columns, or write a script to do this.
(2) In ExportToDatabase, use the SQLite option. Again, you don't need to have a database server setup here. You will need to download a free SQLite viewer tool (e.g. for Mac, sqlitebrowser.app), and then within that tool, you can export your CSVs with headers.
Sorry for the hassle, but hope that helps. We'll be happy if someone wants to add on to ExportToSpreadsheet, or contributes another solution in the interim!