2013 was the last year for the 2500 Suburban. :(
I towed some pretty heavy trailers with my previous half-ton Suburban. 7000ish lbs. My biggest concern about the half-ton trucks is the semifloater rear axle. Knowing what I know now, I would not tow anything heavier than about 6,000 lbs with a half-ton Burb.
The new Suburban HD is a true one ton truck, but it is extremely expensive ($85k) and only gets a 3,000-lb trailer rating from GM. In actuality, with a proper hitch/receiver, it should be able to tow like the old 2000-2006 3/4 ton trucks, probably 12,000 or so.