I've got the same problem and I hate it, because I start PSI solely for the purpose of SIMPLY using the same GPG-key to encrypt communication via Jabber I already have from that person to encrypt mail - something I considered a convenient and useful idea.
As far as I read it, PSI says "jabber supports native encryption via XEP-27 protocol" (seems to be some kind of jabber-gpg connection) and that's what we support and Pidgin has to implement it.
There seems to be "pidgin encrypt" which generates a key pair upon the first start and exchanges own public keys - so no GPG here. The latest release is of May 2007.
URL:
http://sourceforge.net/projects/pidgin-encrypt
(The short answer to your question would therefore be "No".
)