You really expect Nickelodeon to have over 150 episodes of an animated series? Really? Considering the new series is going to be computer animated, episodes are going to take a while to render (and yes, even though computer animation has made a lot of advances in recent years, it'll take time to make them). Though if they get ready by now, on average, they could complete somewhere around 14-26 episodes a season, which probably means the series is in pre-production even as we speak (Nick doesn't announce a series unless they're in the production phase), they could have at least four or five good seasons, a little over 125 episodes, especially if it's successful.
And it is going to air on Nickelodeon proper, not just Nicktoons.
I'm sure next summer, the 4Kids series will find its way on Nick's and Nicktoons' lineups, just to properly prime the audience for the series.
Well, there was a five-year period where the property was completely dormant and a 14-year period where there weren't any theatrical films. Just saying.