He is not too old for nappies! It's best to wait until he's ready, it will happen much quicker and with less hiccups if he's ready. I understand why you want him out of nappies before your next baby arrives, but it could be counterproductive to force the issue.
My son is 3 in a week. He is very aware of his bodily functions but absolutely refuses to wear pants. I think this goes back to a weekend about 4 months ago when we tried potty training. He did fine for two days, then went to nursery and regressed - got VERY angry every time they took him to the loo (the nursery were doing great - taking him regularly, etc) - mainly because he was being distracted from his play. I think he now associates it with that and will not entertain the idea of no nappy. I am having another baby in 3 months and was hoping to have him out of nappies by then - but it is looking increasingly unlikely now. I feel like he is too old for nappies! Help, advice, anyone?