The demand for ORD-TLV really depends on what the connecting traffic for CO's current EWR-TLV offerings looks like. I know that CO90/91 are set up as LAX-EWR-TLV, presumably to capture some piece of the LAX-TLV market, which could just as easily be routed through ORD. Likewise for all other TLV traffic originating west of the Mississippi. With EWR/JFK-TLV flights generally running full (and with reasonably high fares and an excess of demand for cargo capacity) on all three airlines offering the route, adding ORD-TLV could reduce some of the connecting traffic on EWR-TLV, freeing up more space for O/D.

I'm sure that CO and UA are going to look pretty carefully at their proprietary data to figure out if ORD-TLV makes sense as a 744, 772, or 787. Besides, I vaguely recall hearing one time that there's so much demand for cargo on this route that these planes break even before a single passenger ticket is sold, in which case the higher cargo capacity of the 744 would make a lot of sense, whether the 744 runs ORD-TLV or is swapped into EWR-TLV, freeing up the 772 for ORD-TLV...
-JMP