Pushchairs

I've just found out im pregnant with baby #2. It's still very early but of course my mind is going overdrive.

My little boy will be 2.5 years old when little one willl be born.

Do I get a double pushchair?

pushchair that can be single and double?

a single pushchair with buggy board/single and baby carry the newborn?

He doesn't sit much in the pushchair now except if we've been on a long walk and he's tired, or if I go shopping etc.