I don't think you can make valid estimations about the write speed of this new potential format by assuming it'll work at LTO 6 speeds. As density goes up, so does write speed.
Consider LTO 1 through 6:
- LTO1 - 4880 bits/mm, 20 MB/sec
- LTO2 - 7398 bits/mm, 40 MB/sec
- LTO3 - 9638 bits/mm, 80 MB/sec
- LTO4 - 13250 bits/mm, 120 MB/sec
- LTO5 - 15142 bits/mm, 140 MB/sec
- LTO6 - 15143 bits/mm, 160 MB/sec
It seems that doubling storage density yields slightly more than double the speed. (And obviously, like going from LTO5 to LTO6, speed can be increased without any sort of density improvement.) So if we extrapolate that to this new format, at 74 times the density, it perhaps can perform at 74 times the speed, and therefore fill up a tape within a reasonable timeframe. (Which, admittedly, is pure speculation - until actual speed specifications are released for this format, we just don't know.)
But if I was an IT manager, I wouldn't be looking at 185 TB tapes in order to do a full 185 TB local backup every weekend to be sent to an offsite vault. Instead, I'd be looking at 185 TB tapes if I had a remote site, at least 20 miles away, I'm connected to via a fast fiber link, that holds an active replication of my entire 50TB SAN, and I want to store a year's worth of weekly backups, plus a few month's worth of daily backups, in a 40-slot tape library instead of multiple 200-slot tape libraries. Then I could quickly restore almost any file without having to recall tapes, plus have a hot and ready copy of my data in case a flood, fire, earthquake, etc., strikes the primary site. (The logistics of setting up the network, the servers, the SAS connections, etc., not withstanding. :-)
Such a tape isn't for home use or small business use - it's for IBM, Google, Amazon and the like I suspect.