The labor participation rate isn't going to rise very much until the Baby Boomers are institutionalized and/or pass away.
Labor participation rates are based on people under retirement age, therefore boomers retiring has the opposite effect of what you claim, as the number of working age people is decreasing while the number of overall jobs is increasing. From 2008 to early 2017 we had jobs disappearing faster than the boomers could reach 65.