When is 4.3 expected?

I believe you will be OK with stable repos at this stage. Just some notes on what will change in r4.3 final:

  1. Debian 13 Trixie template would be most probably the default Debian template. You will have to download it later (if you need it).
  2. Whonix Gateway & Workstation 18 will be the default. You will need to download them if you need them.

So if you do heavy modifications to your Debian and Whonix templates in rc2, take note of your customization to be able to apply them to the forthcoming new templates.

Otherwise with normal updates, your system should be automatically upgraded to r4.3 stable later.