Why not, they seem to be willing to switch race for no reason on many occasions. I actually like the guy who they picked for Luke Cage.
As for the guy to play Iron Fist, I don't really remember him being memorable on GoT. Hopefully he works out.
As most people have said already, Luke Cage's race is an intergal part of his personality. The reason studios get away with changing the race of white characters is because yes, white characters do far outnumber any other race. But if you take a black character, who's still in the minority, and change his nationality to something else, then you're thinning the already small pool. Bautista playing Luke Cage would be a disaster, because it's downright offensive.
Either way, this conversation took place what, 2 pages ago? Let's just talk about Iron Fist and leave it at that. Anything else will likely result in an endless circle of the same old, same old "argument" for race-bending.