At this point, there might be little choice. We haven't seen enough of Gregory to know if he'll provide the same kind of pass-rushing presence Hardy does, and it doesn't look like Lawrence is going to come close to that at this point. If Lawrence had been tearing it up from left end, then Dallas might could just sit back and see if Gregory can be the right end. However, it's clear at the moment that they do not have another player close to Hardy's caliber.
Lawrence looks like Anthony Spencer to me. People will always be dissapointed with him if they expect him it be this explosive rusher off the edge like Hardy is, like Ware was here, and Gregory can potentially be. He's gotten stronger, but doesn't really have a great array of moves as far as rushing go. He can contain and hold the edge against the run, but he's never gonna be more than a seven or eight sack guy. I think he's solid, but will probably never be spectacular and most second rounders aren't.
We don't need him to be. We already have a superstar pass rusher in his prime and all indications are he'll be a Dallas Cowboy for a long, long time. Gregory has all the tools to be a dominant rusher. In Week 1 some of the moves he showed for a rookie were incredible. In, out, swim moves, spin moves, bull rushes, dipping underneath the shoulder, etc. didn't get much work this week, but if he keeps his head in the clear we will have two dominant edge rushers. Gregory just needs to up his strength so he can hold up against the run.