Not really, but with a little effort you could probably get Automater to do this. You'd have to combine it with some program that lets you mount your Gmail as if it were a remote network drive, and so there's going to be a number of potential pitfalls when it comes to the reliability of your home grown cobbled together system.
I can't say for certain whether or not there's anything similar, but you may want to try looking into alternative IM clients like Adium or Trillian. You may well have better luck finding something to do what you want with those.
Is it possible to automatically back up iChats to Gmail? There used to be a program called Chatalog but it's discontinued now and doesn't work properly (ie. it won't back up archived iChat logs).
So basically anytime somebody sends me an iChat message via my Jabber account, it would somehow be backed up into a Gmail thread. Currently the only method I have of backing up iChats is local log files.
I use something similar to back up my phone's SMS, MMS and call logs and it's called "Backup to Gmail" Just wish there was an iChat equivalent.
Thanks,
-Pete

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