I haven't found anything that points to thing being a limited release
. Least of all on the GW site. Why do you think it will be limited?
I think most assume its going to be limited because thats how GW seem to run there boxed games lately, they release them for varying lengths of time then they go away. So people are naturally assuming that BaC is also limited.
I personaly hope its not limited because its a really nice way to start a force, 1 box puts you in the right direction, 2 gets you well on the way and gives you a usable force and a good points level.