Yeah I don't think they are staying with the six-man but they haven't ruled out a piggyback situation. Either way, Turnbull is likely the long man and they can't completely bury Seranthony. But, just means Kerkering and Marte (who's been pretty solid) need to handle some bigger spots.
What they are also missing is the optionable spot (which was once Ortiz and is technically still Marte) but with pitching this good they haven't needed it.
I still wonder if they have fully committed to Turnbull losing the spot. Which might also cost him money (he has incentives above his $2 million base deal for 12-20 starts and 40-120 innings). Though they could also just tear that up and guarantee him the extra $2 million.
In the end, yes, he'll be needed. And Sanchez is still not a lock either.