I would be amazed if these are less than £400 at launch perhaps £450 with extreme price gouging!
Once word gets out to the mainstream GTX 980 Ti performance for way less money its going to shake up the Nvidia GPU market.
Used Titan X & GTX980Ti prices will nosedive & once there is more GTX1070 stock in the channel any new GTX980Ti stock will drop as its now obsolete.
GTX1070 has 2Gb more VRam + 100W less power draw + lower temps & better thermals makes it hard to justify buying anything else unless you must have the extra performance of the GTX1080!
Why would you buy one at £450 if you can get a 1080 for £524? I can't see them going over £399 and that's for the higher end cards like the MSI gaming