WFC Megatron and Darkmount are Wave 2, ship with more Bumblebee and Prime
WFC Soundwave and Red Alert are Wave 3.

If you miss Wave 1 Thrust and Drift, then you cant get them at this stage in Wave 2 and 3

On topic .. LOVE LOVE LOVE all of these. Well, ok aside from Jolt I love them all
I thought that I was going to have a break from collecting new stuff ...