This is a difficult topic and I truely understand those to hesitate.
I myself have gone through a painful migration that took about a year.
The short answer to the thread topic’s question is:
You will have to go OH2 because there’s no further development and no bug fixing with OH1, and there’s less and less people left to use it (to be able to support you here).
The day will come that you happen to need to have OH2 running for your smart home to work.
This will either be because you need to or want to make changes to your installation and it just doesn’t work in OH1. Or it might turn out you need to move to a new HW, Linux or Java or helper package that no longer works with OH1. For me, those ‘breaking’ changes were the ZWave COLOR and SECURITY commands (those will not be back-ported to OH1).
I know you won’t want to hear and it’s mean to tell, but as a veteran IT pro, I’ve encountered this scheme on a number of occasions.
Let’s face it: the open question is not if this will happen to you but just when.
And the earlier you start the higher your chances are you’re done before you have to be done.
Some hints to at least ease the pain a bit:
Setup a ‘dry’ OH2 w/ full debugging enabled. Simulate running using smarthome:send action in Karaf console. Use this to fix your rules upfront.
Setup OH2 with as many of the ‘big’ OH1 bindings (big in terms of # of devices/items) in compatibility mode as possible.
For the ‘simple’ bindings like astro, ntp etc you can start with OH2 native bindings right away.
Migrate the OH1 bindings to OH2 replacement ones last, one-by-one.
Good luck!