The inline 6 is one of the most reliable engines ever made. The only reliability problems I can think of would be from the turbos but even then you’re talking 100k plus miles. RAM either has such faith in the quality of this engine that they don’t care about completely dropping the Hemi out of the lineup or are gambling with their future/reputation.
I'm sure you're talking more about the diesel applications or even the old 4.0's that were inline 6's but weren't turbo charged.
For this particular application I think the jury is still out. I do think they are gambling a bit but then again they have pretty much told us it's not going to last as long.
What I mean by that is they lowered the powertrain warranty from 100k to 60k on the Hemi for marketing to keep up with the others even though, generally, the Hemi could easily go past 60k without major issues. Now with this more complicated inline 6 has to make it past 60k and there you go that's good enough. Gone are the days of the 3rd gen Hemis easily running past 200k with good maintenance before throwing a major issue.
I am hopeful this new engine does prove itself as I am enjoying my experience with it so far in this Wagoneer L.