Yes, the resignation of David Gregory will hurt Meet the Press, because television is very personality driven. People decide to watch a show because they like the person on the show, not because they like a particular brand. David Gregory is popular and he has a lot of followers that watch the show because of him.
Since the unexpected passing of Tim Russert, Meet the Press has looked to regain the top spot in Sunday morning political talk shows. With David Gregory replacing Russert, Meet the Press has been struggling to have the same engaged audience. With the recent announcement that Chuck Todd will be Gregory's replacement, NBC has the chance to have their slot repeat as top dog in the round table political shows.
I didn't think he was that great of a moderator anyways and Chuck Todd has been on NBC for awhile now and he deserves the promotion. I think he will bring a little bit more outspokeness to Meet the Press that David Gregory was lacking. I think he will ask the tough questions.
The resignation of David Gregory of Meet the Press was a surprise to many. But will it hurt the show, NO. They will easily find another pair of shoes to fill that spot. There are easily 10 people I can think of off the top of my head perfect for the spot.