It seems people just assume a rookie WR can step in and be Golden Tate or 2012 Sidney Rice right away.
The fact is that a lot of rookie WRs end up fairly useless their rookie years. Patton (4th round) had a good pre-season for San Francisco, but he was a complete non-factor during the season, even though he got ample opportunity with Crabtree injured. AJ Jenkins (1st round) was an utter bust for them the year before him.
Lockette isn't a reliable all-game option and probably never will be. He is a gunner and good for an occasional catch. So, unless our rookies shine even though most don't, where are we going to get depth if Harvin or Baldwin go down with injury? We don't have Golden to save us anymore. Do you really want to trot out Kearse, Lockette, and two rookies who may not be physically or mentally prepared to impact the game?
Anyway, it's the same conversation over and over. People forget what Rice can do and naively believe every rookie is going to light up the world from game 1. I specifically remember last year when people thought we'd cut Doug Baldwin after we drafted Chris Harper. There were actually threads on that topic. I'm not saying Rice's spot is assured, but his odds are certainly better than what's being speculated in this thread right now.
That being said, if he's knee's not right or he's actually lost a step, then obviously they have some room to move on. However, I don't believe this notion that he has to beat out Kearse just to make the roster.