I really like Craig as Bond, Casino Royale and Skyfall are both easily in my top 5 Bond movies. I imagine this might be his last go-round with the character, but I think he's been a great fit.
As for that question, a name that has been talked about a lot that I actually think would be a great Bond is Idris Elba, but I think at this point he'd be too old. He's 5 years younger than Craig, which is fine if you're finishing a run of 5 movies as the character, not if you're starting out. By the time he actually has a Bond movie come out, he would be 50 years old, so I think his window has closed. Some potential options I think could work if he is replaced following this next movie would be Tom Hiddleston or Henry Cavill. Tom Hardy would be a good choice, but he's just slightly younger than Elba. Taron Egerton and John Boyega could be in the running down the road, but they are both a little young to take over following Craig.