tdk90: yes, experienced A320 FO got A330, experienced B737NG FO got B777.
As a general rule nowadays people with wide body experience are likely to get onto wide body fleets, all others will go A320 unless very lucky.
Fleet transfers are slower than upgrades, I'm aware of people serving close to 5 years on A320 without fleet transfer ahead (and still alive!).
For B787 no experience exists what they might do, I reckon it will me a mix of external crews with suitable experience (B737NG or wide body) and internal transfers. But transfer from A320 and B777 will be limited as crews are really needed there. Maybe some A330 chaps as their flying reduces.