Dragon Ball Kai, essentially. It caused the franchise to bleed money and saw the revenues for Dragon Ball drop to an all time low in Japan. I think the idea here is to make people remember Dragon Ball Z and not Kai.
Really though, Toei should just bite the bullet and create a brand new series. You can only milk the same stuff for so long before people realize they're playing the same fighter they've played the last three years in a row, just with a slightly different move set. Or that they're buying a slightly different DVD or blu-ray set. Toei is a company that is no stranger to milking things to death by constantly creating new incarnations. I think, if they want Dragon Ball to continue to be profitable, they need a full on new series at some point.
I don't think Toriyama wants to, and that's really (what I think is) a large reason as to why he's making this movie (and on a lesser scale, Yo! Son Goku and Friends Return). I feel that wants to add on to the series without starting a new entry, using movies rather than new shows; after all, he wanted to end Z with the Frieza saga and again with the Cell Saga. He even stated in the manga that he spent so much time on Dragon Ball that he had very little time for his family. Plus, if Toei is in charge of making another Dragon Ball entry, we might get another GT. Though, Toei doesn't have all bad ideas, they did make the very well done "Bardock: The Father of Goku" and "The History of Trunks" (however, the stories for these movies are based off of what is stated by Trunks in the manga and what is stated about Bardock in the manga, writing's not their forte).
Kai was actually very popular due to it's gaining the interest of the original generation and the new generation alike, and everything linked to it sold well as well. The reason they're going for Z rather than Kai is that...well, Z is the complete canon. Various characters do not exist in Kai, most notably the characters introduced after the time skip. It also is many elements and features that were present in both Dragon Ball Z the anime and the manga. As such, it wasn't true to Toriyama nor the fans, despite saying that it was "the original experience". That, and they really have no reason to make a movie for what is essentially just a "cleaner and shorter" version of the original, especially since a movie was just released for the original not too long ago and, by contrast, the original is the more popular incarnation.
On a personal and unrelated note, I, as was pretty much everyone on announcement, was hoping that Kai would be a remake ala Dr.Slump 1997 or Hunter X Hunter 2011, and it was such a darn shame that they simply took the original show, cut some stuff out, made it 16:9 and childproofed it. Granted, it was nice hearing Chris Sabat yell "It's over 9000", what we see in the intro really should have been what was in the show, and that's what people were expecting, a remake instead of a rehash (of a rehash). It's not bad, it's still enjoyable- it's Dragon Ball Z for christ's sake, and it's certainly a heck of a lot better than GT, but there was so much potential that just went to waste. I'm even more shocked that they changed some of the voice actors. It may seem small, but giving #18 a "Cute aloof feminine voice" and giving Gohan a different voice from Kid Goku really misdirects the direction that was given to the characters, and many of the changes were unnecessary, especially since most of the voice actors from the original were still available for casting. Probably the biggest misgiving, however, is that the show advertised that it would "make the fights shorter to make it more like the original", and this was largely because DBZ was seen as a show were people talked and powered up for several episodes before they actually fought (though, after watching the show again uncut, it's really inaccurate)...they didn't do it. I was honestly psyched for at least that much, because I love the manga as well as the anime, but the fights were sometimes FAR longer than they needed to be. I can say wholeheartedly that Kai did not even need to be the almost 100 episodes that it was, they trimmed more of the actual content than they did the fighting...in other words, there was a larger imbalance in filler to content ratio than there was in the original.
R.I.P - Austrailian Jeice ;_;