Due to filming commitments Chris Rankin (Percy Weasley) and Matthew Lewis (Neville Longbottom) have apparently bowed out of appearing at the Florida eXtravaganza convention this month. Both are likely to reprise their roles in Harry Potter and the Order of the Phoenix.
HPANA has confirmed that negotiations are indeed underway but nothing is signed. However, we hear the talks are going "well" and hopes are high.
Thanks to WeasleyNetwork.org for the tip.