These are rumoured and very unconfirmed (particularly the prices). The date has however been mentioned more than once by different sources.
Take the prices with a pinch of salt until we have more news (the 40k Spearhead box looks too high, the price could be wrong. Also, I cannot confirm the box contents yet).
The important bit is the date - much sooner than originally thought - horray !!!!
26-April-2008
Daemons of Chaos Spearhead (English) £105.00 (32 Fig Box + Army Book)
Chaos Daemons Spearhead (English) £160.00 (???) (33 Fig Box + 40k Codex)