Ah, OK. That's on the 5100 so not some issue specific to the 6100 eMMC.
Certainly it's possible it may fail at some point, as any component might. There is no known problem with the 5100 eMMC either though.
The write life of the eMMC, which is what usually concerns people, should be easily sufficient for the expected life if the device in normal use. That will be reduced if the device ends up swapping continually or you have installed packages that create a lot a logs. It can also be extended by installing without SWAP and enabling RAM disks but that is not necessary with eMMC. I only do that on the few test devices I have still running from CF or if I ever run anything from USB directly. Both of which have far far more limited write life.
However, as you say, if for some reason the eMMC does fail it's possible to install an NVMe drive.
Steve