I don't think so. I mean, look at the sequence of events. Everything's going to their satisfaction right up until literally the last minute before release. Chairlifts are working fine, there's video and screenshots, everything's peachy. Then bam, indefinite delay.
To me, this looks like something fundamental to chairlifts had a hidden but seriously bad effect on existing stuff. IOW, chairflifts were working fine in isolation and even, superficially at least, in parks with other stuff. But a closer look showed something seriously wrong, like breaking the rest of the game somehow. We all suspect that Frontier had to change the inner workings of rides, coasters, and/or peeps to make chairlifts function in PC, so my prime suspect is that these changes caused malfunctions elsewhere that only showed up after more extensive testing.
If that's the case, Frontier has 2 main options: fix the chairlift issue or do separate releases. What everybody wants is to make chairlifts play nice with the other stuff in as timely a manner as possible. Frontier seems to be pursuing this option for now, which is a hopeful sign. It means they think they can do this. Also note, even if we end up with separate releases, Frontier will have to do this anyway if we're ever to have chairlifts in the game.
The 2nd option, separate releases, would be a very bad thing to see happen. It would mean that Frontier can't fix chairlifts in a reasonable time, and maybe not ever, so they might end up abandoned. Note that the actual bug here is in the game executable, so merely disabling the chairlift audio and visual assets wouldn't solve the problem. Frontier would have go to back to some pre-chairlift version of the executable, then apply all the bug fixes and any other details required by the other DLC rides, then start over testing that for a while before being able to release it. So this option wouldn't speed up a release, it would only make a release possible at all in the event that chairlifts can't be fixed in a a reasonable time, if ever. And to get chairlifts working, they'd still have to go back and fix the problem they're working on right now (if that's possible). So really, I don't want to see this happen.
So yeah, I know it sucks to have things delayed, especially for folks who really need the bug fixes to work on their big projects. But at least take comfort in the fact that so far, Frontier thinks the problem with chairlifts is fixable and will be done sooner than the other options. That's a really positive sign IMHO.