While I would agree that there seem to be more sellers than buyers for most keys, if you look at ebay you'll see that a lot of them have held their value, and are going for considerably more than original MSRP. Slave Leia, ARC Trooper, General Obi-Wan, Sidious, General Grievous, Yoda, and a few others still command well above the original $35 or so price tag. Sure, you can find a few selling in the $15 - $20 range, but every collectible line is going to have those pieces that don't do well.
As for slowing down, yeah, maybe they haven't been putting quite as many new ones out as they have in the past, but I for one am okay with that. They pushed these out so quickly that a lot of people got overwhelmed and dropped the line, and I think that is a part of why several of them aren't worth half the original price point.
If they continue with the new CW keys in a nicely paced manner, they should do well. And hold their value.