Well from personal experience I was gutted that the old world went pop. But, I understand why it was done.
Furthermore I have several 'classic' army's on square bases and one I've revised for AoS. Now I can still use them (and even if I can't there are other systems I would use them in and enjoy - Kings of War).
However the new forces I collect are going to have relatively new Battle tomes - like the Maggotkin I am enthusiastically collecting and loving it.
Anyway, I am hoping there will be news/rumours on Slaanesh coming back. If anyone has any info I'm all ears.