It's possible to rename a channel status. However, if your leads have progressed to the newly renamed status and it's totally different from what you renamed it to, then it won't make any sense. For instance, if I change the status from Visited web page to Visited landing page, that might not make a difference. But if you're changing Visited web page to Registered or purchased, then I wouldn't do it especially if this campaign is synced in SFDC. It's a pain. If the program/campaign is synced to SFDC and you haven't sent out any outgoing emails, I say it's safe to change it on both Marketo (Channel Status step) and the status steps in SFDC. I hope that helps.