Several people, including Tack, have suggested server mergers as a solution to the problem of consolidating talent. I don't think this will solve the problem. I've been watching the show Numb3rs lately, and I feel inspired to make an analogy which may not actually reflect reality or mathematics.
<Professor Charles Eppes>
Imagine that a WoW server is like a bucket with a hole in it. The people on the server are like drops of water. If you fill up the bucket, water leaks out, and the bucket eventually empties.
A high-end raiding guild is like a plug. You put the plug in the hole, and the bucket stops leaking water.
Merging two low population servers is like pouring water from one leaky bucket into another leaky bucket. The amount of water increases, but the increase is only temporary.
The bucket still has the hole and, without the plug, the bucket will still eventually empty.
</Professor Charles Eppes>
Might work a little bit better with blurry visuals and random fluid dynamic equations being written out with chalk.
The analogy is crude, but you can see why I believe server mergers won't fix the problem. If you're lucky, a server merger may result in the creation of a hardcore guild which revitalizes the server. But that's not guaranteed, and the option for the hardcore to transfer is still very attractive.