I'm not sure anyone can answer this for sure. However, the company is keeping the new hires on not because they are worried about hiring anytime soon, but because they felt it was unfair to kick everyone to the curb with no health insurance and few job prospects right after they quit their old jobs to come to SkyWest. I suspect if you find full time employment elsewhere, no longer need the health insurance, and are unwilling to drop that job as soon as SkyWest is ready for you to return, then they'd expect you to resign. Or at least they'd expect you to go on an unpaid LOA where they aren't continuing to pay you/pay your insurance when you aren't going to be available to them.

They've already fired a number of pilots for taking reserve pay when they knew they weren't actually available to fly if they got called. This would be a very similar situation. You don't want to have to explain getting fired for cause at a mainline interview.

On the other hand, no one would fault you at all for resigning in this situation to take another job or taking an unpaid LOA for the duration of your training requirement, if the company would allow it. You won't, however, keep your seniority I don't believe. You might accrue longevity, but I'm pretty sure you have to pass your LOE before you get to keep your pilot seniority while on an LOA.