Sounds reasonable at this point, without knowing anything about the nextbox and no idea of pricing for that nor the Ps4 you can't really distinguish the two consoles sales-wise imo. Once we have a clearer idea of nextboxes pricing, Ps4 pricing, and stuff like used game blocking, online subscription fee's and potential exclusive content buyouts it will be easier to distinguish them saleswise. Really I see things continuing much like they are now though - with Sony seeing better sales in Japan / Europe and Microsoft making up the difference in the USA.
I see Wii-U struggling to hit the 50M mark but I find it incredibly difficult to judge just how big a difference the big NIntendo games will make once they hit. People are gonna buy the thing for Mario, Mario Kart, Zelda etc and they were behemoth hits on the Wii, but they were all there on the GCN and N64 and neither came close to 50M sales. If there's not a huge price cushion over the competition I see it really struggling, but I wouldn't be surprised to see it have a solid $150 cushion for over a year past the launch of Nextbox / Ps4.