Not really. You'll have to start throwing away those not-quite-deleted
files sometime or the file system will become full. You'll want your 'df'
program to tell you how much space you can use withouth hacking it to first
do "du -s /filesystem/.undelete". The filesystem might want to throw away
some undeletable file which is not the one a userspace really-delete-the-
-next-undeleteable-file program would choose, eg. because it wants to
reduce fragmentation.
If you can live with redoing at most a day's work again, there already is a
perfect undelete method out there. It's called "do a daily backup".
That may not be a perfect solution for everybody, but I for one don't need
anything better.