Every year the Packers always find an undrafted gem who latches onto the 53-man roster out of training camp. Raven Greene and Allen Lazard are two of the most recent examples (though I know Lazard was technically released to the practice squad then brought onto the active roster.) If we look beyond the current roster, players like Sam Shields and Tramon Williams went on to have successful, Super Bowl-winning careers with Green Bay as undrafted players.
This is a strong undrafted free agent class for the Packers, but a lot of guys will have uphill battles in camp already playing at positions with a ton of depth.