Hi there
and welcome to the site.
Is he still napping? What are his nights like, and wake up time?
It could be a bit of separation anxiety, especially with the newborn in the mix, have a read here
http://babywhispererforums.com/index.php?topic=80822.msg697500#msg697500With regards to the toddler bed, I was determined to keep my DS in his cot for as long as possible and I completely dreaded the transition. We made the switch about a month ago (he climbed out of his cot) and it has gone really, really well. We've only had trouble for one nap, and bedtimes are a lot better than before the switch. We were getting all sorts of antics at bedtime (I need a drink, a poo, etc), hence why I thought the toddler bed would be even worse as he could actually get out, but all that has improved and he's actually sleeping for longer (falling asleep a bit earlier, and waking a bit later).
I have also heard many horror stories when it comes to the BBB transition, so I'm not necessarily recommending it, but just offering a bit of hope that it may not be half as bad as you think! Do you need him to be in a toddler bed yet?