This is true. A visitor this week at the UPS gateway at GSO was a head mechanic from Columbia, SC. Greensboro is part of his territory. If anyone in an airline has the inside scooop, it's usually the mechanics.
He said that the next order for freighters would likely be for a load of 747-400Fs. No idea when an order might come, but it sounded like the 747 would fit well into their fleet in the future. Their international operations are really gearing up, so the huge 747s will likely be necessary in a few years.
I asked about a possible UPS 777, but he said that UPS wasn't thinking about that plane too much. It was because of UPS that Boeing made the 757F and the 767F, but it doesn't appear likely that the UPS trend will continue into the 777 line.
I also asked about a possible 757-300F, but he said that UPS wasn't in the market for more 757s just yet. They recently received their last one on order (its sitting in GSO right now) an I think they have a total of 75 now.
I have been off work since having knee surgery but the 747-400 has been in the rumour mill for a while. Alot of people want to see it happen since the 400 has more cargo capacity with a better fuel burn over the existing 100's and 200's in the fleet. As far as orders I haven't seen anything yet though. It would be strange fot the orders to take place at this time with the IPO right around the corner. UPS stock is going public to generate cash for aquisitions. UPS bought Challenge Air Cargo a few months back after partnering with them for years. The reason why was for the exclusive air rights Challenge had. People have been talking about DHL or TNT next. What I expect is UPS to aquire a company that has routes to mainland China from Europe and USA and that also operates 747-400's. It would seem more practical in this matter to do. You would get the routes and also the aircraft. Fed Ex did this with Flying Tigers back in 1989. They aquired the routes and aircraft kept what they needed and sold the rest which a few of the 747's in UPS's fleet are former Fed EX and Flying Tiger aircraft. So far though this has been peoples opinions and rumours. I hope it happens though.