How to transition to big bed

JJ

My 2.5 year old is still in his crib, which I’m fine with, he sleeps great 7 pm - 7:30 am and naps 1:30-3:30 so I don’t really want to upset this amazing-ness. I’m due in March with another boy who will room share with us until September and then we’ll need my sons crib. So we’re not in a rush but just wondering what the best way to do it would be. Put the bed in his room with the crib just to let him get used to it and still sleep in crib? Take the crib totally away one night and put the bed in? I don’t want there to be any sort of jealousy or weird feelings over baby brother “taking” his crib so i feel like a slow transition would be better? He is potty trained during the day but wears a diaper overnight, he doesn’t wake up yet to pee so again, not a huge rush for the bed. Helpppp FTM so nervous about the transition from 1-2 and overthinking all the details.