I don't think we will ever see HL type numbers with CoD, I remember 1000 people online on a Monday evening in il2.
If they are VERY lucky, we will see RoF type numbers, with a couple of servers with 40 people playing in them.
Apart from the state of the game currently, I am also of the opinion that steam is a major turn off to a lot of people.
Not sure what its like with the current patch, but up to now steam was nuking all CoD servers regularly.
Saying that, I started the game up today for the first time in weeks, and it has so much potential, with flashes of absolute brilliance.