Topps has gone ahead with the set. How much they'll produce is anyone's guess, but they had orders from dealers they had to fill (and those dealers likewise had orders from customers). I know a card dealer who has shipped hobby boxes of XFL cards out to his pre-orders, so they've definitely been made.
As jasongeran9 suggested, Topps also did an AAF set, and Topps Now (On Demand) sets for both the AAF and XFL (although the XFL Topps Now set was limited to 30 cards because of the shortened season).
As others have suggested, best guess is that the cards will have their fans, but, much like the old USFL cards, the only long term value will come from players who go on to have successful NFL careers. Unfortunately, I don't think the AAF or XFL are going to generate the types of stars that the USFL did, although I could be surprised. For example, the top QB in the AAF was probably Garrett Gilbert, and his play earned him a NFL contract, but he's the third string guy in Cleveland behind Baker Mayfield and now Case Keenum (Gilbert was the #2 last year) and there's no guarantee he'll even ake the roster, especially if the Browns draft a developmental guy this year. I'd expect them to be more like the WLAF sets from the 1990's.