I think the most important issue today is how we choose our leaders for the future. By this I mean how do organisations identify and select high potential individuals that can be groomed for future leadership. This is a vital and under-researched area.The fact that today's leaders are generally better at getting to the top than leading effectively when they get there demonstrates that we have the wrong system. Selection today is based on qualifications and experience, but rarely on their values, their emotional intelligence or their ability to manage their ego. You can find out much more about this in "Leading Beyond the Ego"
Social media, artifical intelligence and mobile apps has changed people lives. Computer and software have eliminated some jobs and had deep effects on some peopke.These people shape organizations and organizations are getting virtual. Note these environmental changes on organizations
On the high intellectual end of HR issues i would single out the perennial challenge of the last 3 millenia: That of bringing about Attitude Change in a smart way. Hope that this helps.
The effect of Performance management systems (PMS) on employee performance require in-depth research. There is a knowledge gap in this aspect because most organizations lack consistency on employee performance reviews