Jericho will return as a face, that's a lock. Also, it makes sence for him to 'continue where he left off' upon his return - against Cena. Afterall, Cena cost Jericho his job (in kayfabe terms) and that should be addressed. This would allow Cena to turn heel momenterally and Jericho can become the #1 face on Raw. I'm not sure if Jericho would win the title, but WWE would be smart to appease the fans and give him his title reign ... although not straight away.
From there, Jericho should turn heel a few months down the line (once his honeymoon period is over). He is born to be a heel and shines in that role.
Feuds which should happen upon his return:
Jericho / Cena (kayfabe & smark reasons)
Jericho / Kennedy (ultimate promo's)
Jericho / Triple H (storied history)
Jericho / Edge (MUST HAPPEN !!)