The probability of timing chain failure in the N20 engine is difficult to quantify from publicly available data. It is a risk, but not inevitable. There is no reason to believe that the majority of N20 engines from any model year will experience this problem.
What may you do to minimize or address this potential problem? Listen regularly for a change in sound from the engine that may signal timing chain problems and take your vehicle promptly into your service provider if you hear this. Consider having the timing chain guide replaced with the new part, but be aware this is expensive and BMW will not typically cover this expense. You may purchase a warranty to cover the repair costs in event of timing chain failure. Some suggest a shortened oil change interval may help to avoid problems. You may participate in a class action lawsuit in an effort to motivate BMW to provide repairs or an extended warranty.
If you are not comfortable with the risk and steps that may be taken to manage the risk, then it may be time to trade your X3.