In the picture of grot, there is plastic warboss! Or maybe just new warboss model, with kick ass slugga anyway...
AND THEY ARE ALL PLASTIC EXPECT WYRD BOY!
Do you mean the guy with a PK and double-barreled slugga? The sign infront of him says "Nob - by Mike Anderson" - makes me think either Seb P didn't re-cut the boyz sprue and this nob is made from that sprue - or we're getting new nobs too.
Also, we've seen pre-release pics of models before in a grey material that turned out to be the resin they use to cast metal models off of. The trukk and boyz are definitely plastic, not too sure on the others - the tankbustas look like metal models to me.