In general upgrading from 16.04+UCA-Pike -> 18.04 shouldn't be very different to 17.10->18.04.
It is supposed to work.
As you know it is generally a good advise to go with test systems, backups, phased upgrades, ... as there always could be something - but in general yeah, there is noting blocking your usual upgrade path.
If you want test how that would be when 18.04 is out - on a test system take Trusty + UCA-Mitaka (which is on the level of 16.04) and then upgrade to Ubuntu 16.04.
pike would be 3.6 not 3.5 - other than that yes.
In general upgrading from 16.04+UCA-Pike -> 18.04 shouldn't be very different to 17.10->18.04.
It is supposed to work.
As you know it is generally a good advise to go with test systems, backups, phased upgrades, ... as there always could be something - but in general yeah, there is noting blocking your usual upgrade path.
If you want test how that would be when 18.04 is out - on a test system take Trusty + UCA-Mitaka (which is on the level of 16.04) and then upgrade to Ubuntu 16.04.