just want to let you know that they CAN do it. We moved into our house in july and had the girls sharing a big bedroom (dh's idea), then a few weeks later we converted her cot to a bed (dh's idea). if it were not for dh's bravery i had planned to keep liv in her cot until she went to school
. she has not had problems. we had one naptime where she kept getting out and bringing more and more toys and books to bed and i gavce up after 2 hrs of that. but this has not been repeated since. at night the girls SOMETIMES talk for a bit but liv stays in bed (last week alex actually got out and climbed into liv's bed with her).
i think waiting until liv was able to really talk about it helped. she was almost 2 1/2 and we chatted about how she needs to sleep and we play before and after bed but not suring sleepytime. i really thought it would be a struggle and refused to try until dh said to go for it (she had been asking for a bed for ages!)
if things don't work out you could really always use a bassinette for #2 and buy some more time (ages away anyway so might find it is ok)