Each of the Chipmunk movies does worse than the one before.
The first one did moderately well, mainly because it was the first major Chipmunk production we had gotten since Bagdasarian Productions regained control of the franchise after Universal almost ran it into the ground in the 90s, and it kind of resparked an interest in the franchise in general, and sort of reawakened the fandom after they fall into something of mild obscurity. The second movie wasn't as successful as the first, but it did well enough to bring the Chipettes back into the spotlight since they've been a major part of the fracnhise since the 80s, but it got mostly mixed reviews. The third tanked, even David Cross hated doing it, it's gotten mostly negative reviews.
At this point, a fourth one isn't even a question, mainly because that's the direction movies go in nowadays: they just keep going for more and more sequels. I know the actual Chipmunk fandom is really excited about the fourth one simply out of loyalty to the franchise, but I'm sure the general public is moaning, groaning, and belly-aching over this. My only concern is with the new ALVINNN!!! AND THE CHIPMUNKS series being on Nick now with completely different character designs, isnt this going to confuse kids into wondering why they look one way in one thing, and another in another?
At least they took a different route than what was rumored for years what the fourth movie was going to be about"Alvin and the Chipmunks . . . IN SPACE!