Regarding Cubase 8, this is what Carlos Mendoza Rohde (Product Marketing Manager Cubase & Apps) said six weeks ago (04 Sep 2013):
Hello,
I can safely say that Cubase 8 is not coming anytime soon.
Also, we offer usually 4 weeks of grace period, i.e. if you buy the “old” version 4 weeks before the launch of the “new” generation you get the upgrade for free.
Link: http://www.steinberg.net/forums/viewtopic.php?f=180&t=47041&p=303965#p286478