I haven't seen episode five, but I heard it apparently has a higher than normal number of on-screen signs (possibly even showing people messaging each other on their phones?) which need to be understood for the story. So there's more than usual to translate, time, and polish.
I think we've spoken about it before, but personally I'm not bothered if Foundation X never show up again in the main shows/films. They were a poor replacement for Museum in Double, then a stand-in for Neo Shocker in Movie Wars Mega Max, and then I guess very briefly a stand-in for G.O.D. in the Kamen Rider Brave special. So I'm sure that if they turned up again it would be just to do the exact same Shocker-style routine, only with the stunt team dressed as masquerade dopants instead of combatants.
I'd expect it's more likely that Foundation X will turn up in the Double anime, if anything. I'm sure you could look up the plot of the manga if you wanted to find out. Hopefully by virtue of the anime being outside the usual parameters of what Rider to be, they might do something else with it. Or perhaps it will just be a name they throw around from time to time when some random kid is asked who they bought their Memory from.