I would imagine these are like the special upgrade-packs like there is for the EC, WB and NL. I would imagine that the IF will get special figures of their own in a certain future.They look nice. It's just a shame that the Imperial Fist players got screwed over with the pricing. Every other Legion got a separate sculpt for their unique unit. Imperial fist players have a £22 upgrade set they have to buy alongside a £23 unit. That means each of these units costs almost as much as a Primarch. Whereas the Emperors Children, as an example, pay only ~£45 for their unit of 5 terminators.
If I were an imperial fist player, I'd be pleased with the sculpts but raging about the price.
Here are other examples:
Comparing the IF with these, they looks much cheaper and you get much more for the same prices.