Well then if anything they should be deciding based on the performance of 8 and 9. The performance of RO should have no bearing on if they do more Saga films, since they clearly have the ability to do both.
And of course your opinion of the flimsy foundation of TFA is merely your opinion, one that a ton of people disagree with.
Its flimsy. And, assuming its even true, the fact that Disney execs are contemplating a shift would be a potential indicator of their sentiments. Or at least that their ability to sustain production on both ends is not so clear as you claim.