~~Dark Horse does do omnibuses, but they usually aren't out for a year or two. They first do the standard trade-paperback collections, as we've seen so far. After those have been out for a long time, usually to the point that most potential buyers have made their purchase, then they repackage them in Omnibus form. They're typically smaller page sizes, so everything's a little scaled down. I'd predict two omnibuses collecting Initiation and Escalation together, judging by the amount of total issues.~~
~~The only time I've seen them release omnibuses quickly was last year, when their Star Wars license was running out.~~
Nevermind. May 24, 2016.
I got Volume 1 for about 15 or so dollars, so you should probably wait to see if the price goes down again
Halo: Library Edition Volume 1 https://www.amazon.com/dp/1616559071/ref=cm_sw_r_cp_api_i_htzlFbTE972HE
Halo Omnibus Volume 2 https://www.amazon.com/dp/1506710832/ref=cm_sw_r_cp_api_i_WszlFb4DJ352W
They came out with a Library Edition containing the 1st 12 issues, and have another one with the next 12 coming out soon. Both contain writer commentary here and there. So in those specific cases, yes, they're worth the buy.