:copy extension in sieve (RFC3894)

[Stefan]

Hello List!

I want to create a sieve script, which should _copy_  (not move) some Mails to 
another folder or mail-account! I think, at this time this is not supported 
by sieve. But I found this RFC3894
http://www.ietf.org/rfc/rfc3894.txt

Does anybody know, if and when this will be implemented in sieve?
Is there another way to copy different mails to another mailbox?

TIA
Stefan