The dorks over at Airliners.net seem to think an A350F wouldn’t make an appearance until the last half of this decade.
I could easily see FedEx working a package deal w/ Airbus that might include some A350F orders in exchange for the company providing 1.) an Airbus 321F NEO derivative to replace aging 757s at FedEx or 2.) A321F P2F CEO airframes for FedEx in exchange for A350 order.
Airbus needs to sell at least 50 A350s to justify the program.
Airbus A321F NEO or XLR would be a respectable 757 replacement, with comparable weight, range, cargo capacity, and other performance specs. However, it doesn’t exist yet, either. A321 P2F conversions are ramping up, but that aircraft has anemic performance specs compared to a 757F. They’re cheap, though.