The power loss that lead to temperature rise of the part can be calculated as:
Ploss= (Pin-Pout) - Pind = Pout x (1/η-1) - DCR x Iout^2
Where η is efficiency of the converter ; Pind is power loss of the inductor dissipated by the inductor (Pind=DCRxIout^2); DCR is DC resistance of the inductor.
The junction temperature is calculated as: Tj=Ta + θJA x Ploss
Where θJA is thermal resistance (℃/W) (which is 24℃/W for the multi-layer board specified in the datasheet), Ta is ambient temperature (℃).
For example with VOUT=15V, IOUT=2.5A, DCR=50mΩ, η=90%, at Ta=25℃, the estimated junction temperature is:
Ploss = 15 x 2.5 x (1/0.9-1) - 0.05 x (2.5)^2 = 3.85W
Tj = 25 + 24 x 3.85 = 117.4℃
This junction temperature is below 125℃ which is a recommended maximum junction temperature. So, the circuit should be fine.
Although the part can operate with maximumum junction temperature up to 150℃ (Tjmax), it is mentioned in the datasheet that "junction temperature greater than +125°C degrades operating lifetimes".