I think GX is relatively safe as a niche product. Its stilla big BOF SUV, Lexus Landcrusier. There is always room for those. Escalade, Navigator, QX80...
To be honest, i am not sure that GX will survive the next round of Lexus SUVs. IF the RX will have an XL version (similar in size to Highlander), then there is really no need for GX. (Elsewhere, the Prado will be useful, but it would not be beneficial for Lexus to import something that does not sell.) I don't know the numbers, but i would guess that the LX570 outsells the GX460. Correct me if i am wrong.
Even the GX460 now is a "sissified" version of the 4runner because Lexus sees no need for it to be "rough & tough." No low range. No locker. All-wheel drive.
And with EPA beating down the doors on low mileage SUVs, i fear that the GX is on its last leg. Slow sales. 18mpg or so combined MPG with premium gas. Overweight for its purpose (note that BOF does not mean better crash scores either). Limited interior space for its size (3rd row is horrible!). High step in.
Caddy Escalades sell well because they attract certain population of our society. But look at its competitors of same type (ones you listed)...none sell well...and probably on verge of being axed by their respective company.
Toyota is committed to 4runner...but i am not sure that they are committed to GX460.