Taking into account shrinking of old markets and expansion in new ones, I expect 8th gen to be ~10% bigger than 7th, at least for home consoles, and if neither Ninty nor MS give up. Portables will be lucky to tie, and only if Sony manages to boost PSV a lot and Ninty doesn't give up on 2/3DS. Even if current gen portable will tie with last gen, it will take them a lot longer to achieve it, due to PSV bad start and 3DS sales in slow periods a lot lower than DS (during high seasons 3DS does wonders like DS, but outside of it it settles far lower than its awesome dad).