Hi there,
Maybe, it's likely that there are enough inbound links to the old domain, however it is worth checking whether the Domain Redirect that's in place is a 301 or a 302. If it's the later, get it changed to a 301 if you can.
Depending on your access to Google Webmaster Tools, it would be worth informing Google via GWT (if you can) of the change of address (domain) for the old site. This would help to speed up the full reindexing and removal of the old domain from Google's index.
Hope that helps,
Regards, Simon