Of the hubs between the two carriers, only CLE is of lesser importance to the merged carrier, IMHO. I think the three coast hubs (EWR, IAD, & SFO) will play important roles for the merged carrier. ORD is ORD while IAH is important for central & South American flights. That leaves CLE as the vulnerable hub, perhaps it will get downgraded to a focus city.
LAX
I wouldn't be surprised if they decided to downgrade CLE to a focus city... However, as long as DEN is left as a hub, I'll be happy!