Unfortunately, I agree with Elliot 1. I say "unfortunately" because I really would like to see Soliai and Allen come around. Soliai is tremendously strong ... yes he has some athleticism for his size, but it is his raw power that makes him potentially special. His problem is that he isn't dedicated enough. He doesn't work hard on the field, off the field, in the film room ... he just doesn't seem to care enough about his game to take advantage of his athletic ability.
Allen is a different story, he has the ability, but I just question if he has the decision making to play. He makes a lot of outstanding plays as a safety, but I think every coaching staff just sees him as a risk of giving up big plays. So they try him at cornerback, but he's not really quite what is needed in a CB. He's big, fast, but he's just not a great CB. So, I keep hoping he will start to "get it" at S and solve our problem for a ball-hawking playmaker back there ... but apparently it's just not happening for him.
Merling will likely develop nicely, but he's never going to be a brain surgeon either. Luckily, playing a 34 DE doesn't really demand a ton of decision making, and that's the real difference between him ever becoming an OLB or remaining at DE. I think he'll remain at DE where his quickness will make him a 3 down player and allow him to excel.
Langford is a stud. He is going to be a great 34 DE and I'm really pleased with him. He will be a cornerstone of our defense for years to come. :)
I think people are expecting too much from Cam Wake. I hope he turns out to be a good pickup, but if he were a surefire star like many posters here think, then we would have had to pay a lot more for him. I will withold judgement until I see enough of his play to really make a valid determination.
I agree with the OP though, I really hope one or more of these guys step it up next season. My money is on Merling, as his injury set him back in the learning phase, and I'm sure he will really benefit from the extra time to absorb the role and get into shape this offseason.