Hmm.. you're probably right. I think they've been signed for special teams help, but I doubt they make the 53 man roster after the draft and free agency.
The Ravens, more than any team I know, love keeping guys who contribute on special teams even if they don't play in games often. Off the top of my head I can think of Ayanbadejo, Hester, Asa Jackson, Brennen Beyer, and Anthony Levine. I'm sure someone else can think of more. Bottom line, if they are "elite" special teams players, Baltimore wants to find a way to keep them.