Gordon's rehab seems to have gone remarkably well so far. However, I don't think even The Girl who Loved him
could predict how the Cubs' bullpen situation will eventually turn out with any degree of accuracy. The rumors that Alfonseca will be traded to the Angels have died down for the time being, although that's still an option. If the right offer is on the table (for any member of their bullpen), the Cubs will probably make a deal, but that doesn't mean it will definitely happen, especially with a strike/work stoppage looming.
Right now, I'd say the odds of Gordon closing again are just a tad under 50%. It would be a terrific comeback story though, wouldn't it?
Still, unless there are several potential free closers (Leskanic, Zimmerman, possibly Irabu now) just waiting to be grabbed in your league, I'd pick up Escobar with the waiver pick (and Gordon as well, if you have the roster/dl slot to spare), schedule notwithstanding. There will certainly be several more closers who will become available later in the season, but that doesn't mean you shouldn't grab one now. If the players you would be waiting for fall in the Beltre to Dempster range, that's all the more reason to take Escobar, who could presumably be traded for more than that as long as he's collecting saves.
I realize that it's tempting to wait a bit longer for a true gem, but I'd go with the known quantity here. (Easy said when it's not my team, of course...