Plasma just came out with a big bug fix release if only for the major fix to NVIDIA drivers. I was wondering how long does solus usually take to package bug fixes? Do they wait on them like they do with kernels/new desktop versions?

I would guess (and it's only that) about one to two weeks, due to allowing a week in testing. However, since the support of Plasma is not yet official, that may be incorrect.

When time is available and testing can be done, not usually long but it depends on time availability.