Opinions from moms of 2 or more, move toddler to bed or get another crib??

Hi! My son will just have turned 2 when baby arrives. He's still in his crib and I was hoping to keep him there as long as possible because he's active, very smart, very curious and I want him to be safe. His current crib starts as a rolling baby bassinet and I already have the sheets and mattress. I'd hate to buy a new bassinet for next baby, but then that means I need a new crib or maybe toddler bed. I'm wondering if it just makes most sense to get the big boy bed sooner than later to avoid buying double of things we will outgrow soon. I'm just so worried he will escape and hurt himself because he has no fear. For context, our room is on the main floor while the kids' rooms are upstairs with a balcony so I worry about him trying to get down by himself while we are sleeping or unaware somehow. Thoughts or experiences with this? Especially moving a wild toddler to a bed around 2 years. TIA!