If you are already gold now from 30+ stays in 2026, getting A+ now will get you straight to platinum for rest of 2026, and whole of 2027 (i.e. until 31/12/2027). However, if you are gold from spending, then A+ 30 bonus nights might not do much for you in 2026, so you might as well wait until January 2027 to sign up/renew.
The key questions you need to ask yourself in my opinion is whether you want to hit platinum ASAP, and if not, how long it will take you to rack up 30 nights in 2027 - as that is when you will hit platinum in 2027 if you sign up/renew in January 2027.
