Well the 321/322s that will cover the 360 duties are not going to hit the MTIN that the 360s did or near it, so that means you're not going to be able to simply do a like for like replacement of a 360 with a 321 without needing to use a few more units daily that will be in theory be maintenance spares every day.
Saying that with the current suppression of demand, even when taking into account the inferior reliability of the other EMU units, with the 720s on the way and the fact there's been some 321/322s brought in, you'd hope GA wouldn't have any real shortages unless the MTIN of those 321/322s falls away more.