If it gives a good assurance for a good source of income then why not, but as of you know bitcoin after a stable job then as should say that maybe bitcoin is a part of mysideline job .But if in long run if it gives you more than your stable job, then maybe I will stay focus on bitcoin and quit for my day job.
Reasonable answer for this thread, it can be assumed that at the point where you make more from BTC than a real job that there's definately some skill of reading the market(or enough knowledge to make an educated guess of market trends) so if someone gets to that point switching jobs sounds completely reasonable.