I don't know, tbh. There've been no new rumors about the length of the series, though I tend to believe the 30 eps thing because... why else would Ma-kun have said that.

And also, because Decade eats up as much budget in CG/casting/locations/etc for one episode as a regular rider would for two or three, and it's totally showing signs of coughing up at this point already. I don't think they could keep up 50 episodes of this without running Toei/Bandai into the ground. :D;;